buildroot

mpv: fix build on sparc

This commit adds a new patch for mpv that fixes the stdatomic detection
logic so that it realizes linking against libatomic is needed on some
architectures. This fixes the build of mpv on SPARC. The patch has been
submitted upstream.

Fixes:

  http://autobuild.buildroot.net/results/f607eed9a48c4ca00db43f9d2652e615b4bd7c93/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>