hwmon: support ADS79xx family of TI ADCs

Support ADS79xx family of A/D convertors.

Only manual control mode supported at the moment.

Ref: http://www.ti.com/product/ADS7950

Signed-off-by: Nishanth Menon <nm@ti.com>
spidev: introduce a generic spidev DT name

Also make a compatible generic DT name compatible = "linux,spidev"
also to work.

Signed-off-by: Nishanth Menon <nm@ti.com>
HACK: bone dtsi common: hack in ads cape driver in

Signed-off-by: Nishanth Menon <nm@ti.com>
HACK: defconfig: hack in ads cape support

Signed-off-by: Nishanth Menon <nm@ti.com>
HACK: ads79xx: print reg values..

Signed-off-by: Nishanth Menon <nm@ti.com>