power: regulator: lp87565: add regulator support

The driver provides regulator set/get voltage
enable/disable functions for lp87565 family of PMICs.

Signed-off-by: Keerthy <j-keerthy@ti.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>