x86/PB: Clear AP_OFF after PB is initialized
x86/PB: Clear AP_OFF after PB is initialized

This patch clears EC_RESET_FLAG_AP_OFF after the wish is reflected
to the power button state.

It'll prevent the flag from being carried over to RW.

BUG=b:154778457
BRANCH=none
TEST=Verify test_that suite:faft_bios passes.

Signed-off-by: Daisuke Nojiri <fd5f93af191bf7e8f73ea71cc3c0f66b41b1dd49@chromium.org>
Change-Id: I481b986abee66d82a40998154b0536c499ece709
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2213731
Reviewed-by: Aseda Aboagye <12c9b286316a940fd31c24070da5ab64cdd4d0e7@chromium.org>

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