Revert "arm64: zynqmp: Add zynqmp firmware specific DT nodes"

This reverts commit 50a6bd00.

As zynqmp mini emmc does not rely on firmware, remove firmware related
device tree modes from zynqmp mini emmc dts files.

Signed-off-by: T Karthik Reddy <t.karthik.reddy@xilinx.com>
Acked-by: Ashok Reddy Soma <ashok.reddy.soma@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/e69b30d82b0307c563fe72630d9172e53964aeda.1652262769.git.michal.simek@amd.com