spi/pxa2xx: Remove unavailable ssp_type from documentation

Since commit

commit 2f1a74e5
Author: eric miao <eric.miao@marvell.com>
Date:   Wed Nov 21 18:50:53 2007 +0800

    [ARM] pxa: make pxa2xx_spi driver use ssp_request()/ssp_free()

the ssp_type field in struct pxa2xx_spi_master is no longer available.

Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>