xilinx: versal: Add usb dfu/thor distro boot support

Change "dfu_usb" to "usb_dfu" for better representation and change
required macros. Add 60s timeout of dfu-utils to start transaction.
Add support for usb thor to distro boot. Remove DFU_ALT_INFO_RAM
as we use bootcmd_usb_dfu instead of dfu_ram.

Signed-off-by: T Karthik Reddy <t.karthik.reddy@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>