caif: Fix bitmap data type in "struct caifsock"

Bitmap are "unsigned long", so use it instead of a "u32" to make things
more explicit.

While at it, remove some useless cast (and leading spaces) when using the
bitmap API.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>