[INITRD] fix sed file for EXTRA_INIT params in initrd

The {{EXTRA_INIT}} placeholder in the initrd script should be replaced in ${D}/init, not {WORKDIR}/{INITBOOT_NAME}.

Otherwise the replaced version doesn't get installed in the initrd rootfs.

This fixes a USB/Ethernet issue on qcs6490 (USB firmware partition didn't get mounted).

Signed-off-by: Alessandro Pecugi alessandro.pecugi@seco.com