dtc: Remove remaining old-style checks

[Jon Loeliger]

So, like, the other day David Gibson mumbled:
> The remaining old-style tree checking code: check_root(), check_cpus()
> and check_memory() really aren't that useful.  They mostly check for
> the presence of particular nodes and properties.  That's inherently
> prone to false-positives, because we could be dealing with an
> artificial tree (like many of the testcases) or it could be expected
> that the missing properties are filled in by a bootloader or other
> agent.
> 
> If any of these checks really turns out to be useful, we can
> reimplement them later in a better conceived way on top of the new
> checking infrastructure.  For now, just get rid of them, removing the
> last vestiges of the old-style checking code (hoorah).
> 
> Signed-off-by: David Gibson <david at gibson.dropbear.id.au>

Applied.

Thanks,
jdl