keyboard_scan: Update the default scan delay to compensate H1 signal delay
keyboard_scan: Update the default scan delay to compensate H1 signal delay

The default value of the keyboard scan delay was measured at around
2013. That time H1 hadn't been introduced. The keyscan lines go
straightforward to the keyboard matrix.

In recent Chrome OS clamshell/convertible devices, the KSO2 line goes
through H1. It adds more signal delay for inverting the signal. The
default keyboard scan rate seems too fast for the KSO2 line. When an
user presses Refresh key (KSO2, KSI2), EC iterates to assert the next
KSO3, KSO2 still remains asserted that causes T key (KSO3, KSI2)
detected unexpectedly.

Most of the boards override this default value. But a board, which
just uses the default value, may have this Refresh-triggering-T bug.
People debug the same issue over and over again. Should update the
default value and save people time.

BRANCH=None
BUG=b:156007029, b:155696516
TEST=Press Refresh key, only Refresh key detected, no sign of T key.

Change-Id: I5a9ee8058adcac123fdd5500d478913926b00497
Signed-off-by: Wai-Hong Tam <04b587fdf5845741a0c5a8b9cd59ca72d73ef8fc@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2190953
Reviewed-by: Alexandru M Stan <1784cbba6d7675b1eba55eaefe41c7672ad9da3b@chromium.org>
Reviewed-by: Paul Fagerburg <d8c44b60afb21c60f56d931aa690ca1cf34910c8@chromium.org>

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