elf.h: add NT_ARM_PAC{A,G}_KEYS from linux v5.1

to request or change pointer auth keys for criu via ptrace, new in

  linux commit d0a060be573bfbf8753a15dca35497db5e968bb0
  arm64: add ptrace regsets for ptrauth key management

include/elf.h

@@ -683,6 +683,8 @@ typedef struct {
 #define NT_ARM_SYSTEM_CALL	0x404
 #define NT_ARM_SVE	0x405
 #define NT_ARM_PAC_MASK	0x406
+#define NT_ARM_PACA_KEYS	0x407
+#define NT_ARM_PACG_KEYS	0x408
 #define NT_METAG_CBUF	0x500
 #define NT_METAG_RPIPE	0x501
 #define NT_METAG_TLS	0x502