staging: exfat: remove 'file creation modes'

The mode parameter in ffsCreateFile() and create_file() is redundant.
Remove it and definition.

Signed-off-by: Tetsuhiro Kohada <Kohada.Tetsuhiro@dc.MitsubishiElectric.co.jp>
Link: https://lore.kernel.org/r/20200228084037.15123-1-Kohada.Tetsuhiro@dc.MitsubishiElectric.co.jp


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