aarch64: add HWCAP_ definitions from linux v5.0

HWCAP_SB - speculation barrier instruction available added in linux
commit bd4fb6d270bc423a9a4098108784f7f9254c4e6d
HWCAP_PACA, HWCAP_PACG - pointer authentication instructions available
(address and generic) added in linux commit
7503197562567b57ec14feb3a9d5400ebc56812f

arch/aarch64/bits/hwcap.h

@@ -27,3 +27,6 @@
 #define HWCAP_ILRCPC		(1 << 26)
 #define HWCAP_FLAGM		(1 << 27)
 #define HWCAP_SSBS		(1 << 28)
+#define HWCAP_SB		(1 << 29)
+#define HWCAP_PACA		(1 << 30)
+#define HWCAP_PACG		(1UL << 31)