dtc: Fold comment handling test into testsuite

[Jon Loeliger]

So, like, the other day David Gibson mumbled:
> For ages dtc has included a sample dts, comment-test.dts, for checking
> various lexical corner cases in comment processing.  In fact, it
> predates the automated testsuite, and has never been integrated into
> it.  This patch addresses this oversight, folding the comment handling
> test in with the rest of the testsuite.
> 
> Signed-off-by: David Gibson <david at gibson.dropbear.id.au>

Applied.

Thanks,
jdl