ARM: davinci_all_defconfig: Enable TI ADS7950

This enables the TI ADS7950 IIO driver. This is used on LEGO MINDSTORMS
EV3. The other IIO configs removed in this patch are selected by
CONFIG_TI_ADS7950, so they are not actually being desabled.

Signed-off-by: David Lechner <david@lechnology.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>