Currently it's not guaranteed that request struct is not already freed when
reading from it. Fix this by moving synced request related fields from the
pcf50633_adc_request struct to its own struct and store it on the functions
stack.
Signed-off-by: NLars-Peter Clausen <lars@metafoo.de>
Signed-off-by: NSamuel Ortiz <sameo@linux.intel.com>