ARM: Make global handler and CONFIG_MULTI_IRQ_HANDLER mutually exclusive

Even when CONFIG_MULTI_IRQ_HANDLER is selected, the core code
requires the arch_irq_handler_default macro to be defined as
a fallback.

It turns out nobody is using that particular feature as both PXA
and shmobile have all their machine descriptors populated with
the interrupt handler, leaving unused code (or empty macros) in
their entry-macro.S file just to be able to compile entry-armv.S.

Make CONFIG_MULTI_IRQ_HANDLER exclusive wrt arch_irq_handler_default,
which allows to remove one test from the hot path. Also cleanup both
PXA and shmobile entry-macro.S.

Cc: Paul Mundt <lethal@linux-sh.org>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Eric Miao <eric.y.miao@gmail.com>
Tested-by: Jamie Iles <jamie@jamieiles.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 9ad50c4..bd49a6a 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -36,12 +36,11 @@
 #ifdef CONFIG_MULTI_IRQ_HANDLER
 	ldr	r1, =handle_arch_irq
 	mov	r0, sp
-	ldr	r1, [r1]
 	adr	lr, BSYM(9997f)
-	teq	r1, #0
-	movne	pc, r1
-#endif
+	ldr	pc, [r1]
+#else
 	arch_irq_handler_default
+#endif
 9997:
 	.endm