coral: Increase port80 buffer size
coral: Increase port80 buffer size

Bump up port80 buffer size to 256.

(reference: https://chromium-review.googlesource.com/747121)

BUG=None
BRANCH=coral
TEST=Verified that all port80 messages from a boot-up or S3 resume are
present in port80 history buffer.

Change-Id: Ia86807d2373ae7506b7c8ba1801b5ab7aaa927c5
Signed-off-by: Scott Collyer <7d40b3eb9e17bf55d972074a5e77a7ea4159f9dd@google.com>
Reviewed-on: https://chromium-review.googlesource.com/753653
Commit-Ready: Scott Collyer <7d40b3eb9e17bf55d972074a5e77a7ea4159f9dd@chromium.org>
Tested-by: Scott Collyer <7d40b3eb9e17bf55d972074a5e77a7ea4159f9dd@chromium.org>
Reviewed-by: Furquan Shaikh <6be5c96c464778f89679b1062a2e0a6af93d2aa5@chromium.org>

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