s390/xor: Fix xor_xc_2() inline assembly constraints

s390/xor: Fix xor_xc_2() inline assembly constraints

The inline assembly constraints for xor_xc_2() are incorrect. "bytes",
"p1", and "p2" are input operands, while all three of them are modified
within the inline assembly. Given that the function consists only of this
inline assembly it seems unlikely that this may cause any problems, however
fix this in any case.

Fixes: 2cfc5f9ce7f5 ("s390/xor: optimized xor routing using the XC instruction")
Cc: stable@vger.kernel.org
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Link: https://lore.kernel.org/r/20260302133500.1560531-2-hca@linux.ibm.com
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>