btrfs: show compiled-in config features at module load time

We want to know if there are debugging features compiled in, this may
affect performance. The message is printed before the sanity checks.

(This commit message is a copy of David Sterba's commit message when
he introduced btrfs_print_info()).

Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de>
Reviewed-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

fs/btrfs/super.c

@@ -1762,6 +1762,9 @@ static void btrfs_print_info(void)
 #ifdef CONFIG_BTRFS_DEBUG
 			", debug=on"
 #endif
+#ifdef CONFIG_BTRFS_ASSERT
+			", assert=on"
+#endif
 #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
 			", integrity-checker=on"
 #endif