arm64: versal: Add mini eMMC configuration

This patch adds mini eMMC configuration which has only
emmc0 and emmc1 functionalities and can run from small
amount of memory. This is required for memory constraint
devices.

Signed-off-by: Siva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>