x86: Add context value to loapic_mkstub and ioapic_mkstub macros

Add a context value to the ioapic and loapic mkstub macros to allow
the developer to specify a context value that will be passed on the
stack to the interrupt service routines.

All the invocations for the loapic_mkstub and ioapic_mkstub macros
have been changed to pass in 0 so there is no functional difference
ATM.  This change removes the need for drivers to have trampoline ISR
routines to pass a context vaule to their generic ISR routine.

This is the first step in getting rid of the hack where the driver
needs to look into the __initconfig_* linker objects.

Change-Id: I2c5eaa20d8cb5a42ef445762c426854be32c8452
Signed-off-by: Dirk Brandewie <dirk.j.brandewie@intel.com>