Fixes a TCG crash due to attempting the atomic operation without
having set up the address first.  This does not attempt to fix
all of the other missing checks for LOCK.

Fixes: a7cee522
Fixes: https://bugs.launchpad.net/qemu/+bug/1803160Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>
Message-Id: <20181113193510.24862-1-richard.henderson@linaro.org>
Reviewed-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>