Forwarding changes from mfd-next

This patch applies the changes which are present in mfd-next at the moment.
Its taken directly from the tree as a whole from a merge.
MFD: ti_tscadc: disable TSC control

Register bits when TSC not in use

AFE Pen Ctrl and TouchScreen transistors enabling is not

required when only ADC mode is being used, so check for availability of

TSC driver before accessing control register.

This patch is forward ported from the 3.2 based Arago tree maintained
by TI. Original author is Patil, Rachna
IIO: ADC: ti_adc: Fix 1st sample read

Previously we tried to read data form ADC even before ADC sequencer

finished sampling. This led to wrong samples.

We now wait on ADC status register idle bit to be set.

This patch is based on work in the 3.2 based Arago tree
maintained by TI. Original Author is Patil Rachna
iio: ti_am335x_adc: Added iio_voltageX_scale

in_voltageX_scale is supposed to give scaled voltages. This was
missing in the TI driver and has been added for BBB.
Current patch is fixed at a scale for 1.8V AVDD.

Signed-off-by: Zubair Lutfullah <zubair.lutfullah@gmail.com>