KVM: selftests: Assert GICR_TYPER.Processor_Number matches selftest CPU number

KVM: selftests: Assert GICR_TYPER.Processor_Number matches selftest CPU number

The selftests GIC library and tests assume that the
GICR_TYPER.Processor_number associated with a given CPU is the same as
the CPU's selftest index.

Since this assumption is not guaranteed by specification, add an assert
in gicv3_cpu_init() that validates this is true.

Signed-off-by: Maximilian Dittgen <mdittgen@amazon.de>
Link: https://msgid.link/20251119135744.68552-1-mdittgen@amazon.de
Signed-off-by: Oliver Upton <oupton@kernel.org>