avcodec/x86/hevc: added DBF assembly functions

Reviewed-by: James Almer <jamrial@gmail.com>
Reviewed-by: Ronald S. Bultje
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avcodec/x86/hevc: updated to use x86util macros

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