winrt: Fix camera auto rotation

There is no Windows Runtime API to find the camera sensor rotation, so
assume that phones always have a camera mounting of 270 degrees. Tablet
and webcams remain mounted at the default (0 degrees). As the frame is not
flipped automatically by the system, the scan line direction is set to
BottomToTop for front-facing cameras to achieve compatibility with
other platforms.

Task-number: QTBUG-41066
Change-Id: Icf17ecd4aca9fa9d5b24d94e5b21b63ee6f21f28
Reviewed-by: Oliver Wolff <oliver.wolff@theqtcompany.com>
Reviewed-by: Yoann Lopes <yoann.lopes@theqtcompany.com>
winrt: Fix encoding properties

These should match the capture mode. Additionally, there was a semantic
error preventing the encoding properties from being properly selected.
This fixes a bug in which the viewfinder was receiving frames too large
for display as an OpenGL texture.

Task-number: QTBUG-41065
Change-Id: Ia82c8f44bba1692a219edc5f9d78fc76c3d8a4ba
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@theqtcompany.com>
winrt: Add missing QAbstractVideoSurface::stop() call.

This was preventing the surface from restarting with a different format.

Change-Id: I1f86ddb1b16618f167183c7e2fcb32658df578f3
Reviewed-by: Oliver Wolff <oliver.wolff@theqtcompany.com>