Staging/iio/adc/touchscreen/MXS: separate i.MX28 specific register bits

Staging/iio/adc/touchscreen/MXS: separate i.MX28 specific register bits

In order to support i.MX23 and i.MX28 within one driver we need to separate the
register definitions which differ in both SoC variants.

Signed-off-by: Juergen Beisert <jbe@pengutronix.de>
Tested-by: Marek Vasut <marex@denx.de>
Acked-by: Marek Vasut <marex@denx.de>
Tested-by: Lothar Waßmann <LW@KARO-electronics.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
CC: linux-arm-kernel@lists.infradead.org
CC: linux-input@vger.kernel.org
CC: devel@driverdev.osuosl.org
CC: Marek Vasut <marex@denx.de>
CC: Fabio Estevam <fabio.estevam@freescale.com>