erofs: use get_tree_bdev_flags() to avoid misleading messages

Users can pass in an arbitrary source path for the proper type of
a mount then without "Can't lookup blockdev" error message.

Reported-by: Allison Karlitskaya <[e-mail]>
Closes: https://lore.kernel.org/r/CAOYeF9VQ8jKVmpy5Zy9DNhO6xmWSKMB-DO8yvBB0XvBE7=[e-mail]
Signed-off-by: Gao Xiang <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Christian Brauner <[e-mail]>

fs/erofs/super.c

···
 	if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && sbi->fsid)
 		return get_tree_nodev(fc, erofs_fc_fill_super);
 
-	ret = get_tree_bdev(fc, erofs_fc_fill_super);
+	ret = get_tree_bdev_flags(fc, erofs_fc_fill_super,
+		IS_ENABLED(CONFIG_EROFS_FS_BACKED_BY_FILE) ?
+			GET_TREE_BDEV_QUIET_LOOKUP : 0);
 #ifdef CONFIG_EROFS_FS_BACKED_BY_FILE
 	if (ret == -ENOTBLK) {
 		if (!fc->source)