arm64: zynqmp: Wire GEM reset gpio

With ethernet-phy-id driver ETH phy reset can be properly handle that's why
describe it in DT.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/5bfd92827033d19617113f4117f37dcf79699a0f.1662721547.git.michal.simek@amd.com