Fix "W" macro in arch/arm/include/asm/unified.h

Please, fold into 0becb088
aka "Thumb-2: Add macros for the unified assembler syntax"

otherwise:

	crypto/cast6.c:372:39: error: macro "W" passed 2 arguments, but takes just 1

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>