(GTA02, u-boot) time to splash screen reduction

[Werner Almesberger]

I've now reduced the time u-boot spends sampling POWER and AUX from
1s < t <= 2s to 0s < t <= 1s. This means that the splash screen
comes up after about 3.5s, and POWER/AUX can be released at that
time.

It also means that it's now a little easier to unintentionally turn
the device on, but you still need a good dose of bad luck for this
to happen.

Checked in as revision 4297.

- Werner

----------------------------------- Changes -----------------------------------

uboot-gta02.patch:
- board/neo1973/gta02/gta02.c (POWER_KEY_SECONDS): reduced from 2 to 1 second