tee: shm: add page accessor functions

In order to register a shared buffer in TEE, we need accessor
function that return list of pages for that buffer.
Signed-off-by: Volodymyr Babchuk <vlad.babchuk@gmail.com>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>

include/linux/tee_drv.h

@@ -403,6 +403,19 @@ static inline size_t tee_shm_get_size(struct tee_shm *shm)
 	return shm->size;
 }
 
+/**
+ * tee_shm_get_pages() - Get list of pages that hold shared buffer
+ * @shm:	Shared memory handle
+ * @num_pages:	Number of pages will be stored there
+ * @returns pointer to pages array
+ */
+static inline struct page **tee_shm_get_pages(struct tee_shm *shm,
+					      size_t *num_pages)
+{
+	*num_pages = shm->num_pages;
+	return shm->pages;
+}
+
 /**
  * tee_shm_get_page_offset() - Get shared buffer offset from page start
  * @shm:	Shared memory handle