gaia_power: Add power command to check power state.
gaia_power: Add power command to check power state.

It is useful to be able to see the current AP power state, and x86
has a command for this. Add one for gaia.

BUG=chrome-os-partner:11427
TEST=manual
(start with power off)
> powerinfo
off

(press power button)
> [batt] state idle -> pre-charging
AP running ...
Power button released
Setting pwron timer 10038870
powerinfo
on
> Releasing pwron

(after kernel boots, make device go into suspend by typing this at
kernel command line:
type echo mem > /sys/power/state)
> powerinfo
suspend

Change-Id: I3244b3a7fd0b6dd689f3470fb97ffe5a72c8d8f9
Signed-off-by: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/27653
Reviewed-by: David Hendricks <3b0deacc4b5357f519084f1ea34bd42bf5d34545@chromium.org>

fourier49/BIZ_EC,fourier49/BZ_DEV_EC,akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,coreboot/chrome-ec,thehobn/ec,md5555/ec,eatbyte/chromium-ec,coreboot/chrome-ec,fourier49/BIZ_EC,eatbyte/chromium-ec,coreboot/chrome-ec,alterapraxisptyltd/chromium-ec,longsleep/ec,thehobn/ec,coreboot/chrome-ec,thehobn/ec,longsleep/ec,eatbyte/chromium-ec,akappy7/ChromeOS_EC_LED_Diagnostics,fourier49/BZ_DEV_EC,alterapraxisptyltd/chromium-ec,eatbyte/chromium-ec,alterapraxisptyltd/chromium-ec,mtk09422/chromiumos-platform-ec,mtk09422/chromiumos-platform-ec,fourier49/BIZ_EC,gelraen/cros-ec,mtk09422/chromiumos-platform-ec,akappy7/ChromeOS_EC_LED_Diagnostics,fourier49/BZ_DEV_EC,md5555/ec,akappy7/ChromeOS_EC_LED_Diagnostics,longsleep/ec,gelraen/cros-ec,md5555/ec,thehobn/ec,md5555/ec,longsleep/ec,akappy7/ChromeOS_EC_LED_Diagnostics,gelraen/cros-ec,fourier49/BZ_DEV_EC,mtk09422/chromiumos-platform-ec,gelraen/cros-ec,fourier49/BIZ_EC,alterapraxisptyltd/chromium-ec,coreboot/chrome-ec