s390x: Actually use "load on condition" for conditional moves

s390x: Actually use "load on condition" for conditional moves

Although the implementation of the cond_move insn is prepared to emit
"load on condition" instructions, it doesn't, because of a reversed check.
The check is supposed to prevent emitting LOCx instructions when the
condition code mask is set to "always", but it's accidentally negated.
Fix the reversal of the check, so LOCx instructions are actually emitted
when applicable.