sys/membarrier.h: add new constants from linux v5.10

can cause rseq restart on another cpu to synchronize with global
memory access from rseq critical sections, see

  linux commit 2a36ab717e8fe678d98f81c14a0b124712719840
  rseq/membarrier: Add MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ

include/sys/membarrier.h

@@ -9,9 +9,13 @@
 #define MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED 16
 #define MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE 32
 #define MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE 64
+#define MEMBARRIER_CMD_PRIVATE_EXPEDITED_RSEQ 128
+#define MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_RSEQ 256
 
 #define MEMBARRIER_CMD_SHARED MEMBARRIER_CMD_GLOBAL
 
+#define MEMBARRIER_CMD_FLAG_CPU 1
+
 int membarrier(int, int);
 
 #endif