meson: Move riscv64 8bpc only files into bitdepth sources
The cdef.S, itx.S and mc.S files contain only 8bpc implementations and should be compiled only when building with -Dbitdepths=8 configuration.
The cdef.S, itx.S and mc.S files contain only 8bpc implementations and should be compiled only when building with -Dbitdepths=8 configuration.
VideoLAN code repository instance