staging: rts5139: remove unused variable in rts51x_chip.h

the SENSE_TYPE_FORMAT_IN_PROGRESS was checked by rts51x_scsi.c
but never set.

Signed-off-by: Oleksij Rempel <bug-track@fisher-privat.net>
Acked-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>