If CONFIG_MMC_SDHCI_IO_ACCESSORS is defined, the following warning would
shows up:

include/sdhci.h:224: warning: 'struct sdhci_host' declared inside
parameter list
include/sdhci.h:224: warning: its scope is only this definition or
declaration, which is probably not what you want
include/sdhci.h:225: warning: 'struct sdhci_host' declared inside
parameter list
include/sdhci.h:226: warning: 'struct sdhci_host' declared inside
parameter list
include/sdhci.h:227: warning: 'struct sdhci_host' declared inside
parameter list
include/sdhci.h:228: warning: 'struct sdhci_host' declared inside
parameter list
include/sdhci.h:229: warning: 'struct sdhci_host' declared inside
parameter list
Signed-off-by: NLei Wen <leiwen@marvell.com>

Nowdays, there are plenty of mmc driver in uboot adopt the sd standard
host design, aka as sdhci. It is better to centralize the common logic
together to better maintenance.
Signed-off-by: NLei Wen <leiwen@marvell.com>
Acked-by: NAndy Fleming <afleming@freescale.com>