mmal: Add -lm when linking mmal_vout
mmal: Add -lm when linking mmal_vout

This is required since mmal_vout uses the fmod function.

This fixes loading of the mmal_vout plugin on raspbian.

Signed-off-by: Martin Storsjö <54669547a225ff20cba8b75a4adca540eef25858@martin.st>

krichter722/vlc,xkfz007/vlc,krichter722/vlc,vlc-mirror/vlc,vlc-mirror/vlc,krichter722/vlc,xkfz007/vlc,vlc-mirror/vlc,xkfz007/vlc,xkfz007/vlc,krichter722/vlc,xkfz007/vlc,shyamalschandra/vlc,shyamalschandra/vlc,vlc-mirror/vlc,shyamalschandra/vlc,xkfz007/vlc,shyamalschandra/vlc,vlc-mirror/vlc,shyamalschandra/vlc,shyamalschandra/vlc,krichter722/vlc,vlc-mirror/vlc,krichter722/vlc,krichter722/vlc,shyamalschandra/vlc,vlc-mirror/vlc,xkfz007/vlc