arm: kirkwood: Pogo v4: Enable LTO

Enable building Pogo V4 u-boot image with LTO, which results in about 30K
reduction in size.

Rebased to latest master and resend.

Signed-off-by: Tony Dinh <mibodhi@gmail.com>
Reviewed-by: Stefan Roese <sr@denx.de>
1 file changed