exfat: Drop superfluous new line for error messages

exfat_err() adds the new line at the end of the message by itself,
hence the passed string shouldn't contain a new line.  Drop the
superfluous newline letters in the error messages in a few places that
have been put mistakenly.

Reported-by: Joe Perches <joe@perches.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>