staging: bcm2835-camera: Replace deprecated V4L2_PIX_FMT_BGR32

V4L2_PIX_FMT_BGR32 is deprecated as it is ambiguous over where
the alpha byte is. Cheese/GStreamer appear to get it wrong for
one, and qv4l2 gets red and blue swapped.

Swap to the newer V4L2_PIX_FMT_BGRX32 format.

https://www.raspberrypi.org/forums/viewtopic.php?f=38&t=267736&p=1738912



Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>