Added IIO to Kconfig

Took a headache to figure out why the ADC driver isn't loading.
These lines are from the previous 3.8 Kconfig..
Added ADC patches

Started first with a large patch that updated the branch
to the state in mfd-next.
Then added patches for 1st sample read and voltage_scale.
And another fix.
Merge pull request #47 from ZubairLK/3.11

3.11