There is no MMX code for loop filters since commit
6a551f14050674fb685920eb1b0640810cacccf9, so use declare_func
instead of declare_func_emms() to also test that we are not
in MMX mode after return.
Reviewed-by: Ronald S. Bultje <rsbultje@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>