mmc: mv_sdhci: Simplify call to sdhci_mvebu_mbus_config()

This driver already depends on CONFIG_ARCH_MVEBU, so there is no need
to have some checks for this Kconfig symbol in the driver itself. Let's
remove these superfluous checks.

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>