mmc: zynq: rename CONFIG_ZYNQ_SDHCI to CONFIG_MMC_SDHCI_ZYNQ

Make the naming scheme consistent; all SDHCI-base drivers prefixed
with CONFIG_MMC_SDHCI_.

While we are here, add "depends on ARCH_ZYNQ || ARCH_ZYNQMP".

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>