drivers: hwmon: Fix compilation errors in ADC for kernel 4.9

Correct the value of cal_val to pick from right enum. Make
additional changes to fix compilation issues.

Change-Id: I89a83e308da9171f79663951b05678fbe40eb9cf
Signed-off-by: Jishnu Prakash <jprakash@codeaurora.org>
2 files changed