mmc: Fix menuconfig alignment of MMC_SDHCI_* options

Let MMC_SDHCI_BIG_ENDIAN_32BIT_BYTE_SWAPPER depend on MMC_SDHCI. Not
only this is more correct, but this also avoids breaking the alignment
of all other MMC_SDHCI_* options in menuconfig.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Cc: Chris Ball <chris@printf.net>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Albert Herranz <albert_herranz@yahoo.es>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>