uclibc: bump xtensa snapshot version

This new version includes two xtensa fixes:

00571b43df2e libc: posix_fadvise: restore implementation for xtensa
de6561f66693 xtensa: use common ptrace.h

The first fixes (correctly)
http://autobuild.buildroot.net/results/ab1/ab1250c3d402ec3fbaf22eeffd07de218ffafb22/.

The second fixes
http://autobuild.buildroot.net/results/84f/84fb918efbcbf1312a228a9c11608edf096b3c40/

.

The unifdef regression (the original motivation for the fixed xtensa snapshot
version introduced in commit cecaf09c) should now be fixed.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>