staging: r8188eu: remove some structure definitions from wlan_bssdef.h

cmd_msg_parm, H2C_SS_RFOFF_PARAM, joinbssrpt_parm,
P2P_PS_Offload_t and P2P_PS_CTWPeriod_t structures are not used.

Signed-off-by: Ivan Safonov <insafonov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>