clk: qcom: gdsc-regulator: add support for skipping GDSC disable

Some GDSCs have side effects when enabled without first
performing a special reset sequence.  It is only feasible for
this sequence to be performed by the always-on processor (AOP)
when it is resuming from system sleep.  Add support for a device
tree flag which can be specified in order to skip physically
disabling a GDSC when regulator_disable() is called.  The AOP
will then ensure that the GDSC is disabled upon entering system
sleep and appropriately reset upon resuming from system sleep.

Also change the is_enabled() callback so that it returns the
GDSC logical enable state instead of the physical enable state
whenever the disable skipping flag is specified.  This ensures
that all dependent regulator and bus requests are made in the
case of disabling and re-enabling a GDSC without entering system
sleep (i.e. when the GDSC shows up as still physically enabled.)

Change-Id: I0eaa3041daa855e458bf97fc58876bc62a236df2
Signed-off-by: David Collins <collinsd@codeaurora.org>