msm: kgsl: Save and restore coresight debug registers on power collapse

Add shadow registers for the coresight debug registers and save and
restore the values when the GPU goes into power collapse. Reset the
registers to the default initial values when coresight is enabled
and write 0 when it is disabled. If the GPU is power collapsed,
don't wake it up to read and write individual registers while coresight
is enabled.

CRs-fixed: 552580
Change-Id: Ic0dedbad02deac88c50371956c993662f5d34a61
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>