tee: shm: make function __tee_shm_alloc static

The function __tee_shm_alloc is local to the source and does
not need to be in global scope, so make it static.

Cleans up sparse warning:
symbol '__tee_shm_alloc' was not declared. Should it be static?

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>

drivers/tee/tee_shm.c

@@ -112,9 +112,9 @@ static const struct dma_buf_ops tee_shm_dma_buf_ops = {
 	.mmap = tee_shm_op_mmap,
 };
 
-struct tee_shm *__tee_shm_alloc(struct tee_context *ctx,
-				struct tee_device *teedev,
-				size_t size, u32 flags)
+static struct tee_shm *__tee_shm_alloc(struct tee_context *ctx,
+				       struct tee_device *teedev,
+				       size_t size, u32 flags)
 {
 	struct tee_shm_pool_mgr *poolm = NULL;
 	struct tee_shm *shm;