staging:iio:adc:ad7314 removal. Supported via hwmon.

Driver ported over to hwmon where it fits much better.

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Acked-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>