ARM: 8227/1: sa1100: switch to MULTI_IRQ_HANDLER

Add sa1100_handle_irq implementating handle_irq for sa1100 platform.
It is more or less a translation of old assembly code from assembler to
plain C. Also install this irq handler from sa1100_init_irq().

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 89c4b5c..2f3f132 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -703,6 +703,7 @@
 	select GENERIC_CLOCKEVENTS
 	select HAVE_IDE
 	select ISA
+	select MULTI_IRQ_HANDLER
 	select NEED_MACH_MEMORY_H
 	select SPARSE_IRQ
 	help