ubi: Introduce vol_ignored()

This makes the logic more easy to follow.

Signed-off-by: Richard Weinberger <richard@nod.at>

drivers/mtd/ubi/ubi.h

@@ -1105,4 +1105,19 @@ static inline int idx2vol_id(const struct ubi_device *ubi, int idx)
 		return idx;
 }
 
+/**
+ * ubi_is_fm_vol - check whether a volume ID is a Fastmap volume.
+ * @vol_id: volume ID
+ */
+static inline bool ubi_is_fm_vol(int vol_id)
+{
+	switch (vol_id) {
+		case UBI_FM_SB_VOLUME_ID:
+		case UBI_FM_DATA_VOLUME_ID:
+		return true;
+	}
+
+	return false;
+}
+
 #endif /* !__UBI_UBI_H__ */