target/i386: move operand load and writeback out of gen_cmovcc1

target/i386: move operand load and writeback out of gen_cmovcc1

Similar to gen_setcc1, make gen_cmovcc1 receive TCGv.  This is more friendly
to simultaneous implementation in the old and the new decoder.

A small wart is that s->T0 of CMOV is currently the *second* argument (which
would ordinarily be in T1).  Therefore, the condition has to be inverted in
order to overwrite s->T0 with cpu_regs[reg] if the MOV is not performed.

This only applies to the old decoder, and this code will go away soon.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>