release: simplify release script
release: simplify release script

This patch simplifies generation method of artik release
firmware.

Change-Id: I74f76619c7e65caa187c92a0a771c10de4acd7ab
Signed-off-by: Chanho Park <8ec285a53e21b773fd914e03c50e1b6431bc9aa8@samsung.com>

SamsungARTIK/build-artik