clk: qcom: Add support for regulator based GDSC control

Support globally distributed switch controller(GDSC) devices as
regulators. This will enable clients to use the regulator framework
APIs to enable/disable the GDSCs.

The hw_ctrl/domain_ctrl registers which might be required to be
enabled before the GDSC are modelled using syscon framework.

Change-Id: I2d63105d032ab16d5555722680f4371c831823cd
Signed-off-by: Taniya Das <tdas@codeaurora.org>
Signed-off-by: Deepak Katragadda <dkatraga@codeaurora.org>
Signed-off-by: David Dai <daidavid1@codeaurora.org>