mk/image.mk: Ship /init in initramfs

OpenADK's kernel hack to call /sbin/init in initramfs is ugly. Instead,
ship /init as a symlink to /sbin/init. This is safe, since initramfs is
always a filesystem with symlink support.

Signed-off-by: Phil Sutter <phil@nwl.cc>

mk/image.mk

@@ -184,6 +184,7 @@ ${STAGING_TARGET_DIR}/${INITRAMFS}_list: ${TARGET_DIR}/.adk
 		echo "nod /dev/ttyBF1 0660 0 0 c 204 65"; \
 		echo "nod /dev/ttyUL0 0660 0 0 c 204 187"; \
 		echo "nod /dev/ttyUL1 0660 0 0 c 204 188"; \
+		echo "slink /init /sbin/init 755 0 0"; \
 	) >>$@
 
 ${FW_DIR}/${INITRAMFS}: ${STAGING_TARGET_DIR}/${INITRAMFS}_list