uart: Shorten poll timeout to speed up flashing

While firmware upgrades will progress with the poll
timeout at 500ms, it is almost painfully slow. Shortening
it to 1ms makes it feel more like a normal firmware
upgrade.
uart: Fix one of the shadow declaration warnings
main: fix bad getopt setting for -g option

The -g option takes an argument but that was not specified in the
getopt() call.