Revert "arm/h264: fix overreads in h264_chroma_mc8-and-h264_chroma_mc4"

This reverts commit d25f87f5174df5923be7ce0bb89fad08999286ed.

This breaks decoding of some h264 files
I have tested the original patch with fate but by mistake have
forgotten to specify the fate samples so testing was limited to
the internal regression tests.
