FreeBSD: Mark ZFS_MODULE_PARAM_CALL as MPSAFE

ZFS_MODULE_PARAM_CALL handlers implement their own locking if needed
and do not require Giant.

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes #13756

include/os/freebsd/spl/sys/mod_os.h

@@ -52,7 +52,7 @@
 
 #define	ZFS_MODULE_PARAM_CALL_IMPL(parent, name, perm, args, desc) \
     SYSCTL_DECL(parent); \
-    SYSCTL_PROC(parent, OID_AUTO, name, perm | args, desc)
+    SYSCTL_PROC(parent, OID_AUTO, name, CTLFLAG_MPSAFE | perm | args, desc)
 
 #define	ZFS_MODULE_PARAM_CALL(scope_prefix, name_prefix, name, func, _, perm, desc) \
     ZFS_MODULE_PARAM_CALL_IMPL(_vfs_ ## scope_prefix, name, perm, func ## _args(name_prefix ## name), desc)