xorg: bump version of xutil/macros to 1.2.2

This version bump is required by the bump of xlib_libXt from 1.0.5 to
1.0.6 (1.0.6 requires at least xutil/macros 1.2).

The linuxdoc patch is removed, since it has been merged upstream, at
http://cgit.freedesktop.org/xorg/util/macros/commit/?id=e20c503d24e5ccf03035aa0f6d833d235d2179df



The other patch exposing STAGING_DIR is kept, as it is Buildroot
specific. It has just been updated to resolve conflicts.

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