mmc: sdhci: reduce code duplication for aligned buffer

The same code is run for both SDHCI_QUIRK_32BIT_DMA_ADDR and
define(CONFIG_FIXED_SDHCI_ALIGNED_BUFFER).

Unify the code.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>