BugLink: https://bugs.launchpad.net/bugs/1776177

Commit "Kbuild: change CC_OPTIMIZE_FOR_SIZE definition" adds a new
config option CC_OPTIMIZE_FOR_PERFORMANCE, so update the config files
accordingly.
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>