arm64: zynqmp: Add u-boot command to boot into recovery image

arm64: zynqmp: Add u-boot command to boot into recovery image

To boot into the firmware recovery tool, the user currently
needs to press a button on the board while powering the
system up. To simplify this process, a U-Boot command
was added to allow booting directly into the recovery tool.

For example:
ZynqMP> zynqmp reboot <multiboot offset in hex>

Co-develop-by: Prasad Kummari <[email protected]>
Signed-off-by: Prasad Kummari <[email protected]>
Co-develop-by: Michal Simek <[email protected]>
Signed-off-by: Michal Simek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]