ARM: LPC32xx: ADC support for mach-lpc32xx

This patch adds the mach specific support for the LPC32XX ADC driver (the
latter being already in staging/iio)

Signed-off-by: Roland Stigge <stigge@antcom.de>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>