mmc: mv_sdhci: Remove CONFIG_MMC_SDHCI_IO_ACCESSORS support

CONFIG_MMC_SDHCI_IO_ACCESSORS is not supported and/or used by this
driver so let's remove these unused parts completely.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Tom Rini <trini@konsulko.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>