ARM: allow 16-bit instructions in ALT_UP()

Allow ALT_UP() to cope with a 16-bit Thumb instruction by automatically
inserting a following nop instruction.  This allows us to care less
about getting the assembler to emit a 32-bit thumb instruction.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/include/asm/assembler.h

@@ -237,6 +237,9 @@
 	.pushsection ".alt.smp.init", "a"			;\
 	.long	9998b						;\
 9997:	instr							;\
+	.if . - 9997b == 2					;\
+		nop						;\
+	.endif							;\
 	.if . - 9997b != 4					;\
 		.error "ALT_UP() content must assemble to exactly 4 bytes";\
 	.endif							;\