ARM64: zynqmp: Add support for DFU from SPL

ARM64: zynqmp: Add support for DFU from SPL

SPL needs to have bigger stack size because of USB.
Simple malloc needs to be disabled because dfu code requires different
allocation functions. There is no space in OCM that's why random place
in DDR is used.

BOOTD must be disabled because it is causing compilation error.

All variables are disabled and used only variables valid for DFU because
they are simple huge. Including automatic variables added by
CONFIG_ENV_VARS_UBOOT_CONFIG.
Hardcode addresses for u-boot, atf, kernel and dtb
just for SPL DFU code.

Enable SPL DFU for zcu100.
Create new usb_dfu_spl variable just to run Linux kernel loaded in SPL.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>