drm/kselftest: fix spellint typo in test-drm_mm.c

This patch fix a spelling typo in test-drm_mm.c
Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200615121151.1557985-1-standby24x7@gmail.com

drivers/gpu/drm/selftests/test-drm_mm.c

@@ -2483,7 +2483,7 @@ static int __init test_drm_mm_init(void)
 	while (!random_seed)
 		random_seed = get_random_int();
 
-	pr_info("Testing DRM range manger (struct drm_mm), with random_seed=0x%x max_iterations=%u max_prime=%u\n",
+	pr_info("Testing DRM range manager (struct drm_mm), with random_seed=0x%x max_iterations=%u max_prime=%u\n",
 		random_seed, max_iterations, max_prime);
 	err = run_selftests(selftests, ARRAY_SIZE(selftests), NULL);