ENGR00315894-77 mx6: soc: Add vadc power up/down function

ENGR00315894-77 mx6: soc: Add vadc power up/down function

Add vadc power up/down function.
When gis enable in uboot, the CSI0 input mux select setting
to vadc module, clean the bit when gis disabled

Signed-off-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Sandor Yu <R01008@freescale.com>
Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
(cherry picked from commit e0cfa889531d0a2587fb1fc607fffcc9599a2f4e)
(cherry picked from commit 4b8609acf781dab90c6916dea4e74d5ffcd017b3)
(cherry picked from commit 9df6744d8104651801778a023455d0fae939c786)