TFTF: Enable ARMv8.3-PAuth in FWU tests.

This patch adds ARMv8.3-PAuth  support for FWU tests.

Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>
Change-Id: I36a0a2a3870db51cda0a09bd8fd8004e2d01d2bc
diff --git a/include/lib/extensions/pauth.h b/include/lib/extensions/pauth.h
index a4da009..d072f5c 100644
--- a/include/lib/extensions/pauth.h
+++ b/include/lib/extensions/pauth.h
@@ -15,6 +15,9 @@
 
 /* Program APIAKey_EL1 key and enable ARMv8.3-PAuth */
 void pauth_init_enable(void);
+
+/* Disable ARMv8.3-PAuth */
+void pauth_disable(void);
 #endif	/* __aarch64__ */
 
 #endif /* PAUTH_H */