tcg/sparc64: Drop is_64 test from tcg_out_qemu_ld data return

tcg/sparc64: Drop is_64 test from tcg_out_qemu_ld data return

In tcg_canonicalize_memop, we remove MO_SIGN from MO_32 operations
with TCG_TYPE_I32.  Thus this is never set.  We already have an
identical test just above which does not include is_64

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>