drm/selftests: fix spelling mistake "misssing" -> "missing"

There is a spelling mistake in a literal string, fix it.
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20190911091227.5710-1-colin.king@canonical.com

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

@@ -126,7 +126,7 @@ static struct drm_framebuffer_test createbuffer_tests[] = {
 		 .handles = { 1, 1, 0 }, .pitches = { MAX_WIDTH, MAX_WIDTH - 1, 0 },
 	}
 },
-{ .buffer_created = 0, .name = "NV12 Invalid modifier/misssing DRM_MODE_FB_MODIFIERS flag",
+{ .buffer_created = 0, .name = "NV12 Invalid modifier/missing DRM_MODE_FB_MODIFIERS flag",
 	.cmd = { .width = MAX_WIDTH, .height = MAX_HEIGHT, .pixel_format = DRM_FORMAT_NV12,
 		 .handles = { 1, 1, 0 }, .modifier = { DRM_FORMAT_MOD_SAMSUNG_64_32_TILE, 0, 0 },
 		 .pitches = { MAX_WIDTH, MAX_WIDTH, 0 },