qcom: subsys-pil-tz: Correct disabling active clocks/regs in shutdown path

Currently, we disable active clocks and regulators even if
pas_shutdown returns an error. This might cause problems as
the subsystem might still be executing.
Disable these clocks and regulators only if the scm call
to shutdown the subsystem returns without an error.

Change-Id: I782c032d44ee8d311e304df54ce993ab18096644
Signed-off-by: Deepak Katragadda <dkatraga@codeaurora.org>