c2d2: define usart to usb constants
c2d2: define usart to usb constants

All of the c2d2 consoles should be the same size. Define constants and
use them in the queue definitions.

BUG=b:240718978
BRANCH=servo
TEST=none

Change-Id: I69add9f13567833f8563d813cb63c29094845a44
Signed-off-by: Mary Ruthven <81380f3403fed74252e92df3ed012a1819ec6296@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3805280
Reviewed-by: Ziting Shen <6acc76cc59db97fbe94a92a0764cb51c3c29befb@google.com>
Commit-Queue: Ziting Shen <6acc76cc59db97fbe94a92a0764cb51c3c29befb@google.com>

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