selinux: Change bool variable name to index.

security_get_bool_value(int bool) argument "bool" conflicts with
in-kernel macros such as BUILD_BUG().  This patch changes this to
index which isn't a type.

Cc: Paul Moore <paul@paul-moore.com>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Eric Paris <eparis@parisplace.org>
Cc: James Morris <james.l.morris@oracle.com>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Andrew Perepechko <anserper@ya.ru>
Cc: Jeff Vander Stoep <jeffv@google.com>
Cc: selinux@tycho.nsa.gov
Cc: Eric Paris <eparis@redhat.com>
Cc: Paul Moore <pmoore@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Acked-by: David Howells <dhowells@redhat.com>
[PM: wrapped description for checkpatch.pl, use "selinux:..." as subj]
Signed-off-by: Paul Moore <paul@paul-moore.com>