brya/gimble: enable CONFIG_DRIVER_EC_PS8751_FLASH_WINDOW

enable `CONFIG_DRIVER_EC_PS8751_FLASH_WINDOW=y` to speed up FW
update, It only takes 5 seconds to complete the update process
instead of 87 seconds.

BUG=b:271796359
BRANCH=None
TEST=USE="project_gimble emerge-brya coreboot depthcharge"
and retested PD FW update process.

Change-Id: I322b702eb0bf0aab6f84daff5a1a7136bb66ec4b
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/depthcharge/+/4547632
Reviewed-by: caveh jalali <caveh@chromium.org>
Commit-Queue: Mark Hsieh <mark_hsieh@wistron.corp-partner.google.com>
Tested-by: Mark Hsieh <mark_hsieh@wistron.corp-partner.google.com>
1 file changed