x86/jailhouse: Add PCI dependency

Building jailhouse support without PCI results in a link error:

arch/x86/kernel/jailhouse.o: In function `jailhouse_init_platform':
jailhouse.c:(.init.text+0x235): undefined reference to `pci_probe'
arch/x86/kernel/jailhouse.o: In function `jailhouse_pci_arch_init':
jailhouse.c:(.init.text+0x265): undefined reference to `pci_direct_init'
jailhouse.c:(.init.text+0x26c): undefined reference to `pcibios_last_bus'

Add the missing Kconfig dependency.

Fixes: a0c01e4b ("x86/jailhouse: Initialize PCI support")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Link: https://lkml.kernel.org/r/20180115155150.51407-1-arnd@arndb.de