staging: exfat: remove 'vol_type' variable.

staging: exfat: remove 'vol_type' variable.

remove 'vol_type' variable.

The following issues are described in exfat's TODO.
> clean up the remaining vol_type checks, which are of two types:
> some are ?: operators with magic numbers, and the rest are places
> where we're doing stuff with '.' and '..'.

The vol_type variable is always set to 'EXFAT'.
The variable checks are unnessesary, so remove unused code.

Signed-off-by: Tetsuhiro Kohada <Kohada.Tetsuhiro@dc.MitsubishiElectric.co.jp>
Reviewed-by: Mori Takahiro <Mori.Takahiro@ab.MitsubishiElectric.co.jp>
Suggested-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20200130070614.11999-1-Kohada.Tetsuhiro@dc.MitsubishiElectric.co.jp
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>