Reduce the static buffer size from the generic default 1260 down to 64 to match the max FIFO size for the cr50 hardware and reduce the footprint of the driver. BUG=chrome-os-partner:53336 Change-Id: I6f9f71d501b60299edad4b16cc553a85391a1866 Signed-off-by: Duncan Laurie <dlaurie@chromium.org> Reviewed-on: https://review.coreboot.org/16664 Tested-by: build bot (Jenkins) Reviewed-by: Aaron Durbin <adurbin@chromium.org>