omx: always define ENABLE_ST_OMX_{BELLAGIO,TIZONIA}

omx: always define ENABLE_ST_OMX_{BELLAGIO,TIZONIA}

We're trying to be -Wundef clean so that we can turn it on (and
eventually make it an error).

Note that the OMX code already used `#if ENABLE_ST_OMX_BELLAGIO` instead
of #ifdef; I could've changed these, but the point of -Wundef is to
catch typos, so we might as well make the change the right way.

Fixes: 83d4a5d5aea5a8a05be2 "st/omx/tizonia: Add H.264 decoder"
Fixes: b2f2236dc565dd1460f0 "st/omx/tizonia: Add H.264 encoder"
Fixes: c62cf1f165919bc74296 "st/omx/tizonia/h264d: Add EGLImage support"
Cc: Gurkirpal Singh <gurkirpal204@gmail.com>
Signed-off-by: Eric Engestrom <eric.engestrom@imgtec.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>