ext4: fix spelling mistake: "prellocated" -> "preallocated"

Trivial fix to spelling mistake in mb_debug debug message
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

fs/ext4/mballoc.c

@@ -3567,7 +3567,7 @@ void ext4_mb_generate_from_pa(struct super_block *sb, void *bitmap,
 		ext4_set_bits(bitmap, start, len);
 		preallocated += len;
 	}
-	mb_debug(1, "prellocated %u for group %u\n", preallocated, group);
+	mb_debug(1, "preallocated %u for group %u\n", preallocated, group);
 }
 
 static void ext4_mb_pa_callback(struct rcu_head *head)