restore: change type of blk_sigset on k_rtsigset_t

pie/restorer.c: In function ‘restore_thread_common’:
pie/restorer.c:262:39: error: incompatible types when assigning to type
‘k_rtsigset_t’ from type ‘u64’
   RT_SIGFRAME_UC(sigframe).uc_sigmask = args->blk_sigset;
                                       ^
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/restorer.h

@@ -72,7 +72,7 @@ struct thread_restore_args {
 	u32				futex_rla_len;
 
 	bool				has_blk_sigset;
-	u64				blk_sigset;
+	k_rtsigset_t			blk_sigset;
 
 	struct rst_sched_param		sp;