avcodec/hevc_cabac: Rename ff_hevc_transform_skip_flag_decode() to...

avcodec/hevc_cabac: Rename ff_hevc_transform_skip_flag_decode() to hevc_transform_skip_flag_decode()

The function is static and used once in the file its defined in

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>