Presently, init/boot time interrupt delivery mode is enumerated only for
ACPI enabled systems by parsing MADT table or for older systems by parsing
MP table. But for OF based x86 systems, it is assumed & hardcoded to be
legacy PIC mode. This causes a boot time crash for platforms which do not
provide a 8259 compliant legacy PIC.

Add support for configuration of init time interrupt delivery mode for x86
OF based systems by introducing a new optional boolean property
'intel,virtual-wire-mode' for the local APIC interrupt-controller
node. This property emulates IMCRP Bit 7 of MP feature info byte 2 of MP
floating pointer structure.

Defaults to legacy PIC mode if absent. Configures it to virtual wire
compatibility mode if present.
Signed-off-by: Rahul Tanwar <rtanwar@maxlinear.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20221124084143.21841-5-rtanwar@maxlinear.com