x86: Jailhouse port, tested for UART (# 0, polling) and LOAPIC timer

This is an introductory port for Zephyr to be run as a Jailhouse
hypervisor[1]'s "inmate cell", on x86 64-bit CPUs (running on 32-bit
mode). This was tested with their "tiny-demo" inmate demo cell
configuration, which takes one of the CPUs of the QEMU-VM root cell
config, along with some RAM and serial controller access (it will even
do nice things like reserving some L3 cache for it via Intel CAT) and
Zephyr samples:

   - hello_world
   - philosophers
   - synchronization

The final binary receives an additional boot sequence preamble that
conforms to Jailhouse's expectations (starts at 0x0 in real mode). It
will put the processor in 32-bit protected mode and then proceed to
Zephyr's __start function.

Testing it is just a matter of:
  $ mmake -C samples/<sample_dir> BOARD=x86_jailhouse JAILHOUSE_QEMU_IMG_FILE=<path_to_image.qcow2> run
  $ sudo insmod <path to jailhouse.ko>
  $ sudo jailhouse enable <path to configs/qemu-x86.cell>
  $ sudo jailhouse cell create <path to configs/tiny-demo.cell>
  $ sudo mount -t 9p -o trans/virtio host /mnt
  $ sudo jailhouse cell load tiny-demo /mnt/zephyr.bin
  $ sudo jailhouse cell start tiny-demo
  $ sudo jailhouse cell destroy tiny-demo
  $ sudo jailhouse disable
  $ sudo rmmod jailhouse

For the hello_world demo case, one should then get QEMU's serial port
output similar to:

"""
Created cell "tiny-demo"
Page pool usage after cell creation: mem 275/1480, remap 65607/131072
Cell "tiny-demo" can be loaded
CPU 3 received SIPI, vector 100
Started cell "tiny-demo"
***** BOOTING ZEPHYR OS v1.9.0 - BUILD: Sep 12 2017 20:03:22 *****
Hello World! x86
"""

Note that the Jailhouse's root cell *has to be started in xAPIC
mode* (kernel command line argument 'nox2apic') in order for this to
work. x2APIC support and its reasoning will come on a separate commit.

As a reminder, the make run target introduced for x86_jailhouse board
involves a root cell image with Jailhouse in it, to be launched and then
partitioned (with >= 2 64-bit CPUs in it).

Inmate cell configs with no JAILHOUSE_CELL_PASSIVE_COMMREG flag
set (e.g. apic-demo one) would need extra code in Zephyr to deal with
cell shutdown command responses from the hypervisor.

You may want to fine tune CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC for your
specific CPU—there is no detection from Zephyr with regard to that.

Other config differences from pristine QEMU defaults worth of mention
are:

   - there is no HPET when running as Jailhouse guest. We use the LOAPIC
     timer, instead
   - there is no PIC_DISABLE, because there is no 8259A PIC when running
     as a Jailhouse guest
   - XIP makes no sense also when running as Jailhouse guest, and both
     PHYS_RAM_ADDR/PHYS_LOAD_ADD are set to zero, what tiny-demo cell
     config is set to

This opens up new possibilities for Zephyr, so that usages beyond just
MCUs come to the table. I see special demand coming from
functional-safety related use cases on industry, automotive, etc.

[1] https://github.com/siemens/jailhouse

Reference to Jailhouse's booting preamble code:

Origin: Jailhouse
License: BSD 2-Clause
URL: https://github.com/siemens/jailhouse


commit: 607251b44397666a3cbbf859d784dccf20aba016
Purpose: Dual-licensing of inmate lib code
Maintained-by: Zephyr

Signed-off-by: Gustavo Lima Chaves <gustavo.lima.chaves@intel.com>