msm: kgsl: Add missing checks for alloc size and sglen

This reverts commit 44c73103.

In _kgsl_sharedmem_page_alloc():

- Make len of type size_t to be in line with size.
  - Check for boundary limits of requested alloc size before honoring.
    - Make sure sglen is greater than zero before marking it as end
      of sg list.

BUG=27475454

Change-Id: I9053000bf8ca17b4b5237863fe7d3f9a73e811ad

drivers/gpu/msm/kgsl_sharedmem.c

@@ -580,10 +580,15 @@ _kgsl_sharedmem_page_alloc(struct kgsl_memdesc *memdesc,
 			size_t size)
 {
 	int order, ret = 0;
-	int len, sglen_alloc, sglen = 0;
+	int sglen_alloc, sglen = 0;
+	size_t len;
 	void *ptr;
 	unsigned int align;
 
+	size = PAGE_ALIGN(size);
+	if (size == 0 || size > UINT_MAX)
+		return -EINVAL;
+
 	align = (memdesc->flags & KGSL_MEMALIGN_MASK) >> KGSL_MEMALIGN_SHIFT;
 
 	/*