Add Freescale Vybrid vf610 adc driver. The driver only support
ADC software trigger.
VF610 ADC device documentation is available at below reference manual
(chapter 37):
http://cache.freescale.com/files/32bit/doc/ref_manual/VYBRIDRM.pdf?
fpsp=1&WT_TYPE=Reference%20Manuals&WT_VENDOR=FREESCALE&WT_FILE_FORMAT
=pdf&WT_ASSET=Documentation
CC: Shawn Guo <shawn.guo@linaro.org> CC: Jonathan Cameron <jic23@kernel.org> CC: Mark Rutland <mark.rutland@arm.com> CC: Otavio Salvador <otavio@ossystems.com.br> CC: Peter Meerwald <pmeerw@pmeerw.net> CC: Lars-Peter Clausen <lars@metafoo.de> Signed-off-by: Fugang Duan <B38611@freescale.com> Signed-off-by: Jonathan Cameron <jic23@kernel.org>