Revert "kirkwood: disable image for Linksys EA3500 (Audi)"

This reverts commit d9ff499.

At this moment kernel can be fitted in EA3500 image.

Tested by onefreeman (OpenWrt forum user)
Tested-by: Jacks <jack338c@gmail.com> (Github user @jack338c)
Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>

target/linux/kirkwood/image/Makefile

@@ -92,7 +92,6 @@ define Device/linksys_audi
   UBINIZE_OPTS := -E 5
   IMAGE/factory.bin := append-kernel | pad-to $$$$(KERNEL_SIZE) | append-ubi
   BOARD_NAME := linksys-audi
-  DEFAULT := n
 endef
 TARGET_DEVICES += linksys_audi