mfd: Convert all tps65910 allocation to devm_*

Convert memory allocation and regmap initialization to
use devm_* functions.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>