asurada: enable pull down on uart
asurada: enable pull down on uart

H1 can't enable EC uart if UART_H1_TX_EC_RX is always pulled up.

BUG=b:154279402
TEST=flash over ccd works
BRANCH=None

Signed-off-by: Ting Shen <c671d3efec3d7e7e285f3788bf0d1ba4c8605b78@google.com>
Change-Id: Idac8355d5653f9a97e9083f5d23b1c46b2426578
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2159939
Reviewed-by: Eric Yilun Lin <2f2733c7206ea2b76bd2db1905cc5e8a75841c48@chromium.org>
Commit-Queue: Ting Shen <c671d3efec3d7e7e285f3788bf0d1ba4c8605b78@chromium.org>
Tested-by: Ting Shen <c671d3efec3d7e7e285f3788bf0d1ba4c8605b78@chromium.org>

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