[media] uvcvideo: Add GUID for BGR 8:8:8

The Magewell XI100DUSB-HDMI[1] video capture device reports the pixel
format "e436eb7d-524f-11ce-9f53-0020af0ba770".  This is its GUID for
BGR 8:8:8.

The UVC 1.5 spec[2] only defines GUIDs for YUY2, NV12, M420 and I420.
This seems to be an extension documented in the Microsoft Windows Media
Format SDK[3] - or at least the Media Format SDK was the only hit that
Google gave when searching for the GUID.  This Media Format SDK defines
this GUID as corresponding to `MEDIASUBTYPE_RGB24`.  Note though, the
XI100DUSB outputs BGR e.g. byte-reversed.  I don't know if its the
capture device in error or Microsoft mean BGR when they say RGB.

[1]: http://www.magewell.com/hardware/dongles/xi100dusb-hdmi/xi100dusb-hdmi_features.html?lang=en
[2]: http://www.usb.org/developers/docs/devclass_docs/USB_Video_Class_1_5.zip
[3]: http://msdn.microsoft.com/en-gb/library/windows/desktop/dd757532(v=vs.85).aspx



Signed-off-by: William Manley <will@williammanley.net>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>