x86/hevc_deblock: remove some unnecessary instructions

Signed-off-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
x86/hevc_deblock: improve luma functions register allocation

Signed-off-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
x86/hevc_deblock: add add ff_hevc_[hv]_loop_filter_luma_{8, 10, 12}_avx

~5% faster than SSSE3

Signed-off-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>