powerpc: Make PPC_IRQ_SOFT_MASK_DEBUG depend on PPC64

32-bit platforms don't have irq soft masking.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210623032909.826010-1-npiggin@gmail.com

arch/powerpc/Kconfig.debug

@@ -84,6 +84,7 @@ config MSI_BITMAP_SELFTEST
 
 config PPC_IRQ_SOFT_MASK_DEBUG
 	bool "Include extra checks for powerpc irq soft masking"
+	depends on PPC64
 
 config PPC_RFI_SRR_DEBUG
 	bool "Include extra checks for RFI SRR register validity"