kgsl: switch back to allocating from highmem

Commit 344c3acd switched kgsl to allocating
from highmem in page-sized chunks.  While this reduced pressure on highmem, it
may have increased pressure on lowmem to the point where lowmemorykiller
activity due to GFP_KERNEL requests rose.

b/19236185 Phone runs for about day, then apps start getting constantly killed
	   by lowmemorykiller

Change-Id: I92e82cc668cd10d8845d12e7c1bad6d980bc3956
Signed-off-by: Iliyan Malchev <malchev@google.com>

drivers/gpu/msm/kgsl_sharedmem.c

@@ -613,7 +613,7 @@ _kgsl_sharedmem_page_alloc(struct kgsl_memdesc *memdesc,
 	while (len > 0) {
 		struct page *page;
 
-		page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+		page = alloc_page(GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO);
 
 		if (page == NULL) {
 			/*