s390/bitops: Cleanup __flogr()

s390/bitops: Cleanup __flogr()

The flogr() inline assembly has no side effects and generates the same
output if the input does not change. Therefore remove the volatile
qualifier to allow the compiler to optimize the inline assembly away,
if possible.

Also remove the superfluous '\n' which makes the inline assembly appear
larger than it is according to compiler heuristics (number of lines).

Furthermore change the return type of flogr() to unsigned long and add the
const attribute to the function.

This reduces the kernel image size by 994 bytes (defconfig, gcc 15.2.0).

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>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>