Convert most of the remaining "Using plain integer as NULL pointer" sparse
warnings to use NULL.  (Not duplicating patches that are already in -mm,
-bird, or -kj.)

Convert isdn driver struct initializer to use C99 syntax.
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>