Update valve's xpad rework patch

@lrusak originally included this patch http://openelec.tv/forum/20-development-discussion/72352-openelec-test-build-xbox-360-controllers which combines some of valve's steamos kernel work on the xpad driver, so that xbox 360 wireless controllers work a bit more nicely. His patch got outdated when xbox one controller support was added in 3.17 so the patch had to be redone.

I've removed https://github.com/zzattack/OpenELEC.tv/commit/8132b0a4f6390fe9324c2b1eeba69c4c08552274 because it removes support for chinese controllers with VID/PID 0xFFFF. Not sure why it was removed, but I actually own such a controller that needs this :P

In https://github.com/zzattack/OpenELEC.tv/commit/70c76826d1ed04ed503427c20876b8750332cae1 I've also first added a patch to update xpad to the 3.18 version so that hopefully the actual patch in https://github.com/zzattack/OpenELEC.tv/commit/437092d2d536e7d253e78bbb1d19f98e7c5eca03 will remain valid for just a tad longer.

Some positive test results were reported in #2607.