msm: vidc: Restore the threshold registers after GDSC hand offs

This is a software work around for a hardware bug.  Certain venus
threshold registers (normally controlled by TZ) are incorrectly reset
when the decoder subcore GDSC gets turned off (as part of interframe
power collapse).  As a result, bad things happen for decoder secure
sessions.

The fix for this hardware bug exists in two parts:

1) The first part of the fix is that the firmware will not power
collapse the decoder subcore GDSC for secure sessions.

2) However, the GDSC can power collapse on it's own during the brief
moment when we hand off control of the regulator from software to
hardware.  Since this isn't really preventable, we re-program these
registers via a TZ call during the two points at which we suspect the
registers to have been reset.

Change-Id: Iae149310fbac0caf96ed56c9c06bf4f4888c5a5a
Signed-off-by: Shalaj Jain <shalajj@codeaurora.org>