staging: ks7010: Factor out common members in request structs.

Most of the request structures defined in ks_hostif.h have common
members:
* __le16 phy_type;
* __le16 cts_mode;
* __le16 scan_type;
* __le16 capability;
* struct rate_set16_t rate_set;

Factor out these members into a common substructure of type
'hostif_request_t'.  This allows a large portion of the request
initialization code in ks_hostif.c to be factored out into the
'init_request' function.

Signed-off-by: Quytelda Kahja <quytelda@tamalin.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>