arm64: zynqmp: mini-emmc: Added clock configuration in the device tree

arm64: zynqmp: mini-emmc: Added clock configuration in the device tree

This patch added clock configuration for mini emmc in the
device tree and enabled CONFIG_MMC_SDHCI_ZYNQ in defconfig.
Without CONFIG_MMC_SDHCI_ZYNQ, the device was failed to
register. Without this clk configuration, mmc device was
failed to get clk. CONFIG_DOS_PARTITION will be enabled
through Kconfig and hence removed from header file.

After adding all these changes, emmc is working fine.

Signed-off-by: Vipul Kumar <vipulk@xilinx.com>
Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>