cuda USE flag is already handled via use.mask entries in base/ and
amd64/x86 arches. No need to duplicate this on a per-package level.
Thus, remove unnecessary package.use.mask entries.
# Requires yet unavailable >=media-video/ffmpeg-3.3.
>=media-video/mpv-0.23.0 cuda
-# Ilya Tumaykin <itumaykin+gentoo@gmail.com> (19 Jan 2017)
-# x11-drivers/nvidia-drivers is available on amd64.
-media-video/mpv -cuda
-
# Magnus Granberg <zorry@gentoo.org> (18 Jan 2017)
# masked in base, unmask for amd64
>=sys-devel/gcc-6.3.0 -pie
# Requires yet unavailable >=media-video/ffmpeg-3.3.
>=media-video/mpv-0.23.0 cuda
-# Ilya Tumaykin <itumaykin+gentoo@gmail.com> (19 Jan 2017)
-# x11-drivers/nvidia-drivers is available on x86.
-media-video/mpv -cuda
-
# Andreas Sturmlechner <asturm@gentoo.org> (31 Dec 2016)
# on behalf of Andreas K. Hüttel <dilfridge@gentoo.org> (14 Dec 2016)
# Fails to build with newly unmasked ffmpeg-3, so mask this useflag
# xf86-video-??? masked for removal
x11-base/xorg-drivers video_cards_v4l
-# Ilya Tumaykin <itumaykin+gentoo@gmail.com> (19 Jan 2017)
-# Requires x11-drivers/nvidia-drivers available on selected few arches.
-media-video/mpv cuda
-
# Lars Wendler <polynomial-c@gentoo.org> (19 Jan 2017)
# Masked until system heimdal can finally be used with AD DC
net-fs/samba system-heimdal