coresight: enable and disable STM during probe

Enable and disable STM during probe to undo the effect of RPM
temporarily turning on STM to ETF path. This ensures that all
the coresight components from STM to the default compile time
sink (ETF) get disabled in probe thereby resulting in their
states to more closely correspond to their reset states.

This is necessary since coresight drivers are designed to assume
reset state (on a power on boot) for the devices they control.

Change-Id: I8707f6134de2488754fb01b5e2830588efa729cc
Signed-off-by: Pratik Patel <pratikp@codeaurora.org>