s390/asm: Helper macros for flag output operand handling

s390/asm: Helper macros for flag output operand handling

Since gcc supports flag out operands for inline assemblies there is always
the question when this feature should be used and if it is worth all the
ifdefs that come with that.

In order to avoid that provide similar macros like x86 which can be used
for all inline assemblies which extract the condition code. Depending on
compiler features the generated code will either always contain an ipm+srl
instruction pair, which extracts the condition code, or alternatively let
the compiler handle this completely.

Suggested-by: Juergen Christ <jchrist@linux.ibm.com>
Reviewed-by: Juergen Christ <jchrist@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>