baseboard/intelrvp: Enable LTO
baseboard/intelrvp: Enable LTO

We're running low on flash space, so enable LTO.

Before LTO:

RO: 36 bytes in flash and 34972 bytes in RAM still available
RW: 20 bytes in flash and 34972 bytes in RAM still available

After LTO:

RO: 8684 bytes in flash and 35268 bytes in RAM still available
RW: 8604 bytes in flash and 35268 bytes in RAM still available

BRANCH=none
BUG=b:238433667
TEST=make buildall

Signed-off-by: Tom Hughes <fc5c12f30a5ed2baa0581f44ee14ad1eb7b20d83@chromium.org>
Change-Id: I229e7532672f3bdc3040d6b428049a80144cc1e4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3761356
Reviewed-by: Keith Short <f6d578f97033c25f1206cb57d52f358974c82954@chromium.org>

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