tcg: Return bool success from tcg_out_mov

tcg: Return bool success from tcg_out_mov

This patch merely changes the interface, aborting on all failures,
of which there are currently none.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>