dtoc: Detect drivers which do not parse correctly

dtoc: Detect drivers which do not parse correctly

At present if a driver is missing a uclass or compatible stirng, this
is silently ignored. This makes sense in most cases, particularly for
the compatible string, since it is not required except when the driver
is used with of-platdata.

But it is also not very helpful. When there is some sort of problem
with a driver, the missing compatible string (for example) may be the
cause.

Add a warning in this case, showing it only for drivers which are used
by the build.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Walter Lozano <walter.lozano@collabora.com>