staging: exfat: remove unnecessary parentheses

Fix checkpatch.pl warning:

	CHECK: Unnecessary parentheses around ...

Signed-off-by: Roi Martin <jroi.martin@gmail.com>
Link: https://lore.kernel.org/r/20191030010328.10203-2-jroi.martin@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>