powerpc/irq: Mark check_return_regs_valid() notrace

check_return_regs_valid() is called from the middle of the irq exit
handling, which is all notrace, so mark it notrace also.

Reported-by: Sachin Sant <sachinp@linux.ibm.com>
Link: https://lore.kernel.org/all/4C073F6A-C812-4C4A-BB7A-ECD10B75FB88@linux.ibm.com/


Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230406122118.3760344-1-mpe@ellerman.id.au