brcmfmac: aggregate dongle ram access interface

For fullmac chips host driver can access to dongle RAM through SDIO function 1.
Introduce brcmf_sdio_ramrw and place it at bcmsdh.c with other interface
functions.

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