common: board_[read/write]_serial weak reference cleanup

board_read_serial and board_write_serial were prototyped as weak
and this made all instances, that included that prototype, weak
as well.  In order to not lose information from the prototype,
default and override functions, I changed to use the override
weak marker symbols.

These functions defaulted for specific configurations as
different functionality and used an #ifdef tree to do this. I
made these a single definition for each function and used
IS_ENABLED instead of the #ifdef tree.  I also added a
definition for the case that the configuration would not have
produced a function.

BUG=none
BRANCH=none
TEST=make buildall -j

Change-Id: Ie41c53f3a17d665358e46eefd3ded3066ee80a7d
Signed-off-by: Denis Brockus <dbrockus@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1631583
Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-by: Jett Rink <jettrink@chromium.org>
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Commit-Queue: Jett Rink <jettrink@chromium.org>

0 files changed, 0 insertions, 0 deletions