volteer: enable link time optimization
volteer: enable link time optimization

Enable LTO to save code space.

BUG=none
BRANCH=none
TEST=make buildall
TEST=verify Volteer boots and verify PD charging and type C device
detection.

Change-Id: Icc1684a05675f3c5b3d0fc3f75aadea63d16d3a8
Signed-off-by: Keith Short <f6d578f97033c25f1206cb57d52f358974c82954@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2029191
Reviewed-by: Abe Levkoy <2e1ad7039298f93262cf06bbb457275fb3e2ecb5@chromium.org>

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