os-release: Add COREOS_BOARD variable
os-release: Add COREOS_BOARD variable

os-release is requested in bug reports, and knowing which board
the problem occurred on is often helpful.

Signed-off-by: Geoff Levand <c3918f39022407dee6a0056ceca9b1aa80e8e4ce@infradead.org>

coreos/scripts,glevand/coreos--scripts,coreos/scripts,glevand/coreos--scripts