arm64: zynqmp: Add label to GPIO lines for boot mode and POR

Add label to GPIO lines controlling boot mode and POR EMIO pins so System
Controller can assert those lines on Versal.

Signed-off-by: Saeed Nowshadi <saeed.nowshadi@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>