mwifiex: minor cleanup in multiport aggregation

'mp_data_port_mask' and 'mp_end_port' gives correct information
even for the chipsets supporting SDIO new mode (32 ports).
We will get rid of this chip specific handling.

Signed-off-by: Amitkumar Karwar <akarwar@marvell.com>
Signed-off-by: Avinash Patil <patila@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>