KVM: s390: Use try_cmpxchg() instead of cmpxchg() loops

Convert all cmpxchg() loops to try_cmpxchg() loops. With gcc 14 and the
usage of flag output operands in try_cmpxchg() this allows the compiler to
generate slightly better code.

Acked-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Acked-by: Janosch Frank <frankja@linux.ibm.com>
Link: https://lore.kernel.org/r/20241126102515.3178914-2-hca@linux.ibm.com


Signed-off-by: Heiko Carstens <hca@linux.ibm.com>