dtc: Fix recognition of whitespace characters

[Jon Loeliger]

So, like, the other day David Gibson mumbled:
> At present, the lexer in dtc recognizes only space, tab and newline as
> whitespace characters.  This is broken; in particular this means that
> dtc will get syntax errors on files with DOS-style (CR-LF) newlines.

Doctor, it hurts when I use DOS. :-)

> This patch fixes the problem, using flex's built-int [:space:]
> character class.
> 
> Signed-off-by: David Gibson <david at gibson.dropbear.id.au>
> ---
> 
> Jon, please apply.

Applied.

Thanks,
jdl