exfat: don't print error log in normal case

When allocating a new cluster, exFAT first allocates from the
next cluster of the last cluster of the file. If the last cluster
of the file is the last cluster of the volume, allocate from the
first cluster. This is a normal case, but the following error log
will be printed. It makes users confused, so this commit removes
the error log.

[1960905.181545] exFAT-fs (sdb1): hint_cluster is invalid (262130)

Signed-off-by: Yuezhang Mo <Yuezhang.Mo@sony.com>
Reviewed-by: Andy Wu <Andy.Wu@sony.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>