apparmor: sparse fix: add apparmor.h to lib.c

Fix the following sparse warnings:
security/apparmor/lib.c:37:6: warning: symbol 'aa_split_fqname' was not declared. Should it be static?
security/apparmor/lib.c:63:6: warning: symbol 'aa_info_message' was not declared. Should it be static?
security/apparmor/lib.c:83:6: warning: symbol 'kvmalloc' was not declared. Should it be static?
security/apparmor/lib.c:123:6: warning: symbol 'kvfree' was not declared. Should it be static?

Signed-off-by: James Morris <jmorris@namei.org>