arm64: zynqmp: Add gpio labels for modepin gpio

Using label helps with better chip identification.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/12b2fcd94e528c8ca7117f6741aae36b5942b430.1683034376.git.michal.simek@amd.com