multimedia/libvpx: kill all options
None of the consumers were tested with non-default options. As
there're no additional dependencies users are better off with
Makefile.local which provides access to more e.g.
--enable-better-hw-compatibility --enable-onthefly-bitpacking --enable-error-concealment --enable-coefficient-range-checking --enable-postproc-visualizer
Similar to multimedia/aom this reduces maintenance.