staging: exfat: remove redundant if statements

If statement does not affect results when updating directory entry in
ffsMapCluster().

Signed-off-by: Tetsuhiro Kohada <Kohada.Tetsuhiro@dc.MitsubishiElectric.co.jp>
Link: https://lore.kernel.org/r/20200302095716.64155-2-Kohada.Tetsuhiro@dc.MitsubishiElectric.co.jp


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