matchbox-panel-2: bump srcrev to fix compile warnings

matchbox-panel-2: bump srcrev to fix compile warnings

The older versions of matchbox-panel were naively using -Werror which causes
warnings with gcc 4.6 (which were patched away) and again more with gcc 4.8.
I'd already fixed this upstream so bump the srvrev and drop the patch.

(From OE-Core rev: ae38cac225f0d84e6acecb6bc46df939d37cd031)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>