ARM: show_regs: on v7-M there are no FIQs, different processor modes, ...
ARM: show_regs: on v7-M there are no FIQs, different processor modes, ...

no indication about irqs in PSR and only a single ISA. So skip the whole
decoding and just print the xPSR on v7-M.

Also mark two static variables as __maybe_unused to prevent the compiler
from emitting:

	arch/arm/kernel/process.c:51:20: warning: 'processor_modes' defined but not used [-Wunused-variable]
	arch/arm/kernel/process.c:58:20: warning: 'isa_modes' defined but not used [-Wunused-variable]

Signed-off-by: Uwe Kleine-König <181323dd666a182bc2d953e52d0ac3ab54cd8391@pengutronix.de>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs