Restore PAuth context in case of unknown SMC call

Change-Id: I8fb346743b7afddbb8bf5908db4f27ee5a26f99b
Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>
diff --git a/bl31/aarch64/runtime_exceptions.S b/bl31/aarch64/runtime_exceptions.S
index aa9d007..c295176 100644
--- a/bl31/aarch64/runtime_exceptions.S
+++ b/bl31/aarch64/runtime_exceptions.S
@@ -419,6 +419,9 @@
 	 */
 	mov	x0, #SMC_UNK
 	str	x0, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_X0]
+#if CTX_INCLUDE_PAUTH_REGS
+	bl	pauth_context_save
+#endif
 	b	restore_gp_registers_eret
 
 smc_prohibited: