drm/vkms: Fix missing kmalloc allocation failure check

Currently the kmalloc allocation for config is not being null
checked and could potentially lead to a null pointer dereference.
Fix this by adding the missing null check.

Addresses-Coverity: ("Dereference null return value")
Fixes: 2df7af93 ("drm/vkms: Add vkms_config type")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Sumera Priyadarsini <sylphrenadin@gmail.com>
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210115130911.71073-1-colin.king@canonical.com

drivers/gpu/drm/vkms/vkms_drv.c

@@ -188,7 +188,11 @@ static int vkms_create(struct vkms_config *config)
 
 static int __init vkms_init(void)
 {
-	struct vkms_config *config = kmalloc(sizeof(*config), GFP_KERNEL);
+	struct vkms_config *config;
+
+	config = kmalloc(sizeof(*config), GFP_KERNEL);
+	if (!config)
+		return -ENOMEM;
 
 	default_config = config;