checkpatch: do is not a possible type

A do without braces '{' may trigger a false possible type 'do' and then
this may be interpreted as an external definition of foo():

	do
		foo();
	while (bar);

Add do to the type exclusions.  Fix up tests so we can check for them.

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>