security/apparmor/apparmorfs.c: conditionally compile get_loaddata_common_ref()

security/apparmor/apparmorfs.c: conditionally compile get_loaddata_common_ref()

Some config did this:

security/apparmor/apparmorfs.c:177:28: warning: 'get_loaddata_common_ref' defined but not used [-Wunused-function]
  177 | static struct aa_loaddata *get_loaddata_common_ref(struct aa_common_ref *ref)

get_loaddata_common_ref() is only used if
CONFIG_SECURITY_APPARMOR_EXPORT_BINARY=y.

(Or of course move the function into that block if maintainers perfer)

Fixes: 8e135b8aee5a0 ("apparmor: fix race between freeing data and fs accessing it")
Cc: John Johansen <john.johansen@canonical.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: John Johansen <john.johansen@canonical.com>