scsi: csiostor: Fix NULL check before debugfs_remove_recursive

debugfs_remove_recursive() has taken the null pointer into account.  Remove
the null check before debugfs_remove_recursive().

Link: https://lore.kernel.org/r/20191026195625.GA22455@saurav


Signed-off-by: Saurav Girepunje <saurav.girepunje@gmail.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>