checkpatch: values: double ampersand may be unary

It is possible to use double ampersand (&&) in unary context where it
means the address of a goto label.  Handle spacing for it.

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>