sys/prctl.h: add PR_PAC_RESET_KEYS from linux v5.0

aarch64 pointer authentication code related prctl that allows
reinitializing the key for the thread, added in linux commit
ba830885656414101b2f8ca88786524d4bb5e8c1

include/sys/prctl.h

@@ -146,6 +146,13 @@ struct prctl_mm_map {
 #define PR_SPEC_DISABLE (1UL << 2)
 #define PR_SPEC_FORCE_DISABLE (1UL << 3)
 
+#define PR_PAC_RESET_KEYS       54
+#define PR_PAC_APIAKEY (1UL << 0)
+#define PR_PAC_APIBKEY (1UL << 1)
+#define PR_PAC_APDAKEY (1UL << 2)
+#define PR_PAC_APDBKEY (1UL << 3)
+#define PR_PAC_APGAKEY (1UL << 4)
+
 int prctl (int, ...);
 
 #ifdef __cplusplus