checkpatch: check spacing for square brackets

Check on the spacing before square brackets.  We should only allow spaces
there if this is part of a type definition or an initialialiser.

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>