gaia_power: Report power on reason
gaia_power: Report power on reason

Report the reason for a power on, to assist with debugging.

BUG=chrome-os-partner:11307
BRANCH=snow
TEST=manual
Build and boot on snow
See that power on reason is now reported

> 0.003508 power on 2
[0.028674 AP running ...]
...
12.163780 ending loop 2
Shutdown complete.
[batt] state discharging -> idle
17.801167 power on 4
Overriding CHARGER_INT with CHARGER_INT on EXTI4
[17.825873 AP running ...]
17.826071 XPSHOLD seen
[batt] state idle -> discharg

Change-Id: I2044419b330a74d19d8c4e63fa8853aa477b4df1
Signed-off-by: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/32301
Reviewed-by: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>

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