arm64: zynqmp: Check 0 node ID

ID is decimal not hexadecimal that's why passing hex number all the time
end's up as 0 that's why check it. Node ID 0 is not valid anyway.
Also properly say it in help.

Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/68c5cd5eade216f3c5aa6eb703ee9f69f14acad1.1685615549.git.michal.simek@amd.com
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