brcm80211: fmac: move sdio used statistics to struct brcmf_sdio

Some statistics only used by sdio modules. Move them to sdio layer
private structure brcmf_sdio. This is part of the fullmac bus
interface refactoring.

Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Arend van Spriel <arend@broadcom.com>
Reviewed-by: Alwin Beukers <alwin@broadcom.com>
Signed-off-by: Franky Lin <frankyl@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>