The combining of SDHCI_TRANSFER_MODE and SDHCI_COMMAND writes is only
required for esdhc, but not necessarily for usdhc.  Different from
esdhc where the bits for transfer mode and command are all in the same
register CMD_XFR_TYP, usdhc has a newly introduced register MIX_CTRL
to hold transfer mode bits.  So it makes more sense to separate transfer
mode from command write for usdhc.
Signed-off-by: NShawn Guo <shawn.guo@linaro.org>
Tested-by: NDirk Behme <dirk.behme@de.bosch.com>
Signed-off-by: NChris Ball <cjb@laptop.org>