kms: Return a negative error code in kms_bo_create()

The function returns returns 0 on success or a negative value in case of an
error, except when given invalid attributes in which case it returns the
positive EINVAL value. Replace that with -EINVAL to allow the caller to detect
errors with a < 0 check.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jakob Bornecrantz <wallbraker@gmail.com>

libkms/api.c

@@ -80,7 +80,7 @@ int kms_bo_create(struct kms_driver *kms, const unsigned *attr, struct kms_bo **
 			type = value;
 			break;
 		default:
-			return EINVAL;
+			return -EINVAL;
 		}
 	}