clk: qcom: gdsc-regulator: use mode control for disable skipping feature

If the disable skipping feature is allowed in device tree, then
use regulator_set_mode() to control the feature's usage at
runtime.  This is needed for SM8150 gpu_cx_gdsc in order to
facilitate GMU hang recovery.

REGULATOR_MODE_NORMAL (default) --> physical GDSC disable skipped
REGULATOR_MODE_IDLE             --> physical GDSC disable occurs

Change-Id: I7eac1cbdd3f505d96bdffd30a7e8b36bcaafb26e
Signed-off-by: David Collins <collinsd@codeaurora.org>