clk: msm: gdsc: Add API to allow clearing CORE & PERIPH memory

In the cases where periph and core memory bits will be required to be
retained unless modem/low-power-audio subsystem are out of reset.

The boolean property 'qcom,disallow-clear' associated with a GDSC will
allow retaining the memory bits. Once modem & lpass subsystem are out of
reset the api 'gdsc_allow_clear_retention' will be invoked for the reuqired
GDSC from the respective pil client driver.

Change-Id: I331e04c6fd4ea43b10a534d063f288431c158791
Signed-off-by: Taniya Das <tdas@codeaurora.org>