Move vars from rtw_recv.h to rtw_recv.c in order to prevent unused vars warnings when including rtw_recv.h

Note that "SNAP_ETH_TYPE_APPLETALK_DDP", "SNAP_ETH_TYPE_TDLS", "SNAP_HDR_APPLETALK_DDP", "oui_8021h" and "oui_rfc1042" are still unused and can be commented out.