Allow override of device asserts, including multi-device support.

Set in board file with TARGET_OTA_ASSERT_DEVICE.
(cherry-picked from commit 0f452f2)

Change-Id: I3d06bdc0e3e26bde0c0e646accd050364f9713b9
add no_assets.option
Change-Id: I489e7b965aa2e4286ebacd64006522a5d206f2db