iio: adc: mcp320x: Add compatible with vendor prefix to OF table

The driver Device Tree binding now documents compatible strings that have
a vendor prefix, so add these to the OF device ID table to match and mark
the old ones as deprecated explaining that should not be used anymore.

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Acked-by: Michael Welling <mwelling@ieee.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>