brcmfmac: use platform specific alignment in SDIO

The SDIO part of the brcmfmac driver uses a static define BRCMF_SDALIGN
to align buffers used for SDIO transfers. This patch replaces it by
using alignment derived from the platform specific data.

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