(GTA02, u-boot) wait-for-power patch update

[Werner Almesberger]

I added Matt's ADC generalization and his power good check, and also
added polling for the wall charger. The complete patch is here:

http://svn.openmoko.org/trunk/src/target/u-boot/patches/wait-for-power-DONTUSE.patch

Andy, if you're still up, can you please comment if you agree with
the changes to pcf50633_read_charger_type ? I've moved the ID resistor
detection after the USB/adapter detection, such that we don't boot if
the charger is connected but has no power, or, perhaps worse, something
else and strange is there.

wait-for-power-DONTUSE.patch:
- drivers/misc/pcf50633.c (pcf50633_adc_read, pcf50633_read_charger_type): 
  applied the rest of Matt's 3.6V threshold changes
- board/neo1973/gta02/gta02.c (wait_for_power): added threshold checking, as
  suggested by Matt
- board/neo1973/gta02/gta02.c (wait_for_power, poll_charger): look for the 
  charger and enable 1A charging if found
- drivers/misc/pcf50633.c (pcf50633_read_charger_type): test for charger/USB
  power before looking for the ID resistor
- include/pcf50633.h: for a change, declare prototypes

The patch goes to the end of series. I think the wait_for_power loop
is pretty self-explanatory. We basically wait until we've found at
least one good power source, and blink the red LED while waiting.

Note that this doesn't change that u-boot is blissfully ignorant of
what happens if USB is disconnected while waiting.

- Werner