ARM64: Enable CONFIG_GENERIC_IRQ_SHOW_LEVEL

Since several interrupt controllers including GIC support both edge and
level triggered interrupts, it's useful to provide that information in
/proc/interrupts even on ARM64 similar to ARM and PPC.

This is based on Geert Uytterhoeven's commit 7c07005e ("ARM: 8339/1:
Enable CONFIG_GENERIC_IRQ_SHOW_LEVEL")
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/Kconfig

@@ -31,6 +31,7 @@ config ARM64
 	select GENERIC_EARLY_IOREMAP
 	select GENERIC_IRQ_PROBE
 	select GENERIC_IRQ_SHOW
+	select GENERIC_IRQ_SHOW_LEVEL
 	select GENERIC_PCI_IOMAP
 	select GENERIC_SCHED_CLOCK
 	select GENERIC_SMP_IDLE_THREAD