scripts/patch-kernel: digest kernel.org hosted .xz patches

kernel.org is hosting patches and kernel compressed with xz (lzma2+).
Allow scripts/patch-kernel to decompress these files.
Signed-off-by: NShawn Landden <shawnlandden@gmail.com>
Signed-off-by: NMichal Marek <mmarek@suse.cz>

scripts/patch-kernel

@@ -116,6 +116,10 @@ findFile () {
 		ext=".bz2"
 		name="bzip2"
 		uncomp="bunzip2 -dc"
+  elif [ -r ${filebase}.xz ]; then
+                ext=".xz"
+                name="xz"
+                uncomp="xz -dc"
   elif [ -r ${filebase}.zip ]; then
 		ext=".zip"
 		name="zip"