grunt: Reduce PD turn off delay
grunt: Reduce PD turn off delay

Reduce PD_POWER_SUPPLY_TURN_OFF_DELAY to 30 milliseconds. Thanks
to PPC VBUS discharge, VBUS drops below 0.8V (vSafe0V) in well
under 10 milliseconds.

Also remove TODO comments for adjusting PD values, since these
all appear correct now.

BUG=b:69683108,b:69683178
BRANCH=grunt
TEST=check VBUS rise and fall on scope

Change-Id: I506851e13850dddda97ae9582a5c0aa7d66882c3
Signed-off-by: Edward Hill <db1406b34e091703092b6b136bdfeb2c8125fc0e@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1259385
Reviewed-by: Jett Rink <9d4aef0593e6843318d99df31597fb6153b89787@chromium.org>

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