drm/ttm: Fix memory leak in ttm_agp_backend.c

This patch fix a memory leak found by cppcheck.
[drivers/gpu/drm/ttm/ttm_agp_backend.c:129]:
(error) Memory leak: agp_be

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>
diff --git a/drivers/gpu/drm/ttm/ttm_agp_backend.c b/drivers/gpu/drm/ttm/ttm_agp_backend.c
index 3302f99e..764be36 100644
--- a/drivers/gpu/drm/ttm/ttm_agp_backend.c
+++ b/drivers/gpu/drm/ttm/ttm_agp_backend.c
@@ -126,6 +126,7 @@
 	agp_be->ttm.func = &ttm_agp_func;
 
 	if (ttm_tt_init(&agp_be->ttm, bdev, size, page_flags, dummy_read_page)) {
+		kfree(agp_be);
 		return NULL;
 	}