bump(sys-kernel/coreos-firmware): Update to new snapshot

This includes new bnx2x firmware required by linux 3.15:
 * Missing firmware: bnx2x/bnx2x-e2-7.8.19.0.fw (bnx2x.ko)
 * Missing firmware: bnx2x/bnx2x-e1h-7.8.19.0.fw (bnx2x.ko)
 * Missing firmware: bnx2x/bnx2x-e1-7.8.19.0.fw (bnx2x.ko)