enabling W=1 by default

[Andy Shevchenko]

Hi!

looking at the redness of the output of `make W=1` here is the question:
isn't it a good time to enable `make W=1` by default. Yes, I understand
the impact, but at least we can do it mandatory for a _new_ code submitted to
U-Boot, right?

Ideally I would have what Linux kernel has for a few releases already, i.e.
Werror by default and getting close to make a clean builds with that and
make W=1` at least against default configurations (yeah, with U-Boot there is
probably no default, but sandbox one).

-- 
With Best Regards,
Andy Shevchenko