ryu: workaround MAX77620 shutdown issue
ryu: workaround MAX77620 shutdown issue

When shutting down the MAX77620 PMIC by asseting its SHDN pin, the
EN_PP3300 output of the PMIC (GPIO3) is not going off keeping the PP3300
rail up. Workaround that issue by removing the pull-up on EN_PP3300 when
we assert SHDN.

Signed-off-by: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>

BRANCH=none
BUG=chrome-os-partner:38689
TEST=on a P5 board, type "apshutdown" and see the power state machine
going to S5, type "powerbtn" and see it going back to S0.

Change-Id: I0e5fba6da118d931b07fff58088604ee00a6bcdd
Reviewed-on: https://chromium-review.googlesource.com/263958
Trybot-Ready: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>
Tested-by: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>
Reviewed-by: Alec Berg <1a4429eeda29095a12e19a73405f80f5b7f37a63@chromium.org>
Commit-Queue: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>

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