Build initramfs network boot image

Now that we can build network boot initramfs image, let's stop building
the over-sized initrd image.

BUG=chrome-os-partner:17368
TEST=Network boot and install.
CQ-DEPEND=CL:42108

Change-Id: I3a87c962d16f6d8d18041e666f1206f2656e67ab
Signed-off-by: Vic Yang <victoryang@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/42095
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
1 file changed