pchg: Initialize pchg chips on startup
pchg: Initialize pchg chips on startup

This patch makes pchg task disable the interrupt on shutdown and
initialize pchg chips on start-up.

Tested as follows:

1. Run dut-control power_state:on -> off -> on.
2. Run dut-control power_state:reset.

Do 1 and 2 with and without a stylus attached and verify pchg task
remains under control.

BUG=b:176725734, b:173235954
BRANCH=trogdor
TEST=CoachZ

Signed-off-by: Daisuke Nojiri <fd5f93af191bf7e8f73ea71cc3c0f66b41b1dd49@chromium.org>
Change-Id: I0b1b5501975ad6c8a89041639d3fa90a71b4e9b5
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2643586
Reviewed-by: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec