dtc: Disable semantic checks by default

[Jon Loeliger]

So, like, the other day David Gibson mumbled:
> At present, dtc makes a lot of semantic checks on the device tree by
> default, and will refuse to produce output if they fail.  This means
> people tend to need -f to force output despite failing semantic checks
> rather a lot.
> 
> This patch splits the device tree checks into structural checks (no
> bad or duplicate names or phandles) and semantic checks (everything
> else).  By default, only the structural checks are performed, and are
> fatal.  -f will force output even with structural errors (using this
> in -Idts mode would essentially always be a bad idea, but it might be
> useful in -Idtb mode for examining a malformed dtb).
> 
> Semantic checks are only performed if the new -c command line option
> is supplied, and are always warnings only.  Semantic checks will never
> be performed on a tree with structural errors.
> 
> This patch is only a stopgap before implementing proper fine-grained
> error/warning handling, but it should at least get rid of the
> far-too-frequent need for -f for the time being.
> 
> This patch removes the -f from the dtc testcases now that it's no
> longer necessary.
> 
> Signed-off-by: David Gibson <david at gibson.dropbear.id.au>

Applied.

jdl