vc1: Fix intensity compensation performance regression

Introduced by 28243b0d35b47bbf9abbd454fc444a6e0a9e7b71

Intensity compensation is always used once it was encountered, because
v->next_use_ic is never set back to zero.

Reset v->next_use_ic, when resetting v->next_luty/uv.

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
Merge remote-tracking branch 'qatar/master'

* qatar/master:
  vc1: Fix intensity compensation performance regression

Conflicts:
	libavcodec/vc1.c

See: ed5bed4152203aed8cce01a679bed67bbda8903f
Merged-by: Michael Niedermayer <michaelni@gmx.at>
Convert XvMC to hwaccel v3

Signed-off-by: Ivan Kalvachev <ikalvachev@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>