artik5: add reference its file for verified boot
artik5: add reference its file for verified boot

This patch adds a reference its file for artik5 and verified
boot. The file will be located in prebuilt directory.

Change-Id: I8698090689ae23a22f68a847f1b4c5f9013dedea
Signed-off-by: Chanho Park <8ec285a53e21b773fd914e03c50e1b6431bc9aa8@samsung.com>

SamsungARTIK/build-artik