samus: avoid waking extpower task until task has been initialized
samus: avoid waking extpower task until task has been initialized

Fix booting without battery by avoiding waking the extpower task
until it has run extpower_board_hacks() the first time.

The problem was if there was no battery and AC was attached,
extpower_board_hacks() would run twice on boot, once in extpower
task initialization, before the while(1) loop, and a second time
due to the AC_PRESENT interrupt. This would cause
extpower_board_hacks() to think that AC had transitioned from 1
to 1, which represents a glitch on ACOK, so it would disable
charging, thus causing us to lose power.

BUG=chrome-os-partner:35570
BRANCH=samus
TEST=load on a samus and boot with and without battery

Change-Id: Idf6d0022f7dbedbb66a2fbe1c2b7dd885eabc43b
Signed-off-by: Alec Berg <1a4429eeda29095a12e19a73405f80f5b7f37a63@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/250301
Reviewed-by: Shawn N <5259333ce42e3ace6a73988cec7115ed9d3a661a@chromium.org>
Reviewed-by: Duncan Laurie <70662b43bc1a20b57ded72a2b08be88dd0da4841@chromium.org>

md5555/ec,akappy7/ChromeOS_EC_LED_Diagnostics,md5555/ec,fourier49/BIZ_EC,coreboot/chrome-ec,coreboot/chrome-ec,fourier49/BZ_DEV_EC,fourier49/BIZ_EC,fourier49/BIZ_EC,coreboot/chrome-ec,coreboot/chrome-ec,eatbyte/chromium-ec,fourier49/BZ_DEV_EC,coreboot/chrome-ec,akappy7/ChromeOS_EC_LED_Diagnostics,akappy7/ChromeOS_EC_LED_Diagnostics,fourier49/BZ_DEV_EC,akappy7/ChromeOS_EC_LED_Diagnostics,akappy7/ChromeOS_EC_LED_Diagnostics,eatbyte/chromium-ec,fourier49/BIZ_EC,eatbyte/chromium-ec,md5555/ec,coreboot/chrome-ec,md5555/ec,eatbyte/chromium-ec,fourier49/BZ_DEV_EC