msm: kgsl: Store process mem entries in a rbtree

The list of memory objects attached to a process gets searched quite
a lot during normal operation of the driver.  For processes with a
lot of memory allocations, the linear search through the list is O(N)
and uses a lot more CPU during critical loops than it should. Change
the mem entry list to a rbtree for faster search speeds.

Change-Id: Ic0dedbad1b25d9d77f56f93696b2fe933fbad333
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
diff --git a/drivers/gpu/msm/kgsl.h b/drivers/gpu/msm/kgsl.h
index 20ed808..3dafbb9 100644
--- a/drivers/gpu/msm/kgsl.h
+++ b/drivers/gpu/msm/kgsl.h
@@ -132,7 +132,7 @@
 	int memtype;
 	int flags;
 	void *priv_data;
-	struct list_head list;
+	struct rb_node node;
 	uint32_t free_timestamp;
 	/* back pointer to private structure under whose context this
 	* allocation is made */