msm: kgsl: Add a new API to allow sharing of GPU performance counters

Adreno uses programmable performance counters, meaning that while there
are a limited number of physical counters each counter can be programmed
to count a vast number of different measurements (we refer to these as
countables).  This could cause problems if multiple apps want to use
the performance counters, so this API and infrastructure allows the
counters to be safely shared.

The kernel tracks which countable is selected for each of the physical
counters for each counter group (where groups closely match hardware
blocks). If the desired countable is already in use, or there is an
open physical counter, then the process is allowed to use the counter.

The get ioctl reserves the counter and returns the dword offset of the
register associated with that physical counter.  The put ioctl
releases the physical counter.  The query ioctl gets the countables
used for all of the counters in the block - up to 8 values can be
returned.  The read ioctl gets the current hardware value in the counter

Change-Id: Ic0dedbadae1dedadba60f8a3e685e2ce7d84fb33
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Carter Cooper <ccooper@codeaurora.org>