mfd: Add support for tps65910 device sleep

Adding support for device sleep through the external input control
signal "SLEEP".
Changing the SLEEP signal state can switch the device into SLEEP and
ACTIVE state.
Also adding sleep configuration for different resources so that they
should be keep on during sleep state of device.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>