BL31: Enable pointer authentication support

The size increase after enabling options related to ARMv8.3-PAuth is:

+----------------------------+-------+-------+-------+--------+
|                            |  text |  bss  |  data | rodata |
+----------------------------+-------+-------+-------+--------+
| CTX_INCLUDE_PAUTH_REGS = 1 |  +192 | +1536 |   +0  |   +0   |
|                            |  0.3% |  3.1% |       |        |
+----------------------------+-------+-------+-------+--------+
| ENABLE_PAUTH = 1           | +1848 | +1536 |  +16  |   +0   |
|                            |  3.3% |  3.1% |  3.1% |        |
+----------------------------+-------+-------+-------+--------+

Results calculated with the following build configuration:

    make PLAT=fvp SPD=tspd DEBUG=1 \
    SDEI_SUPPORT=1                 \
    EL3_EXCEPTION_HANDLING=1       \
    TSP_NS_INTR_ASYNC_PREEMPT=1    \
    CTX_INCLUDE_PAUTH_REGS=1       \
    ENABLE_PAUTH=1

Change-Id: I43db7e509a4f39da6599ec2faa690d197573ec1b
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/include/bl31/bl31.h b/include/bl31/bl31.h
index 08c555d..3deb0a5 100644
--- a/include/bl31/bl31.h
+++ b/include/bl31/bl31.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2018, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2019, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -12,6 +12,8 @@
 /*******************************************************************************
  * Function prototypes
  ******************************************************************************/
+void bl31_setup(u_register_t arg0, u_register_t arg1, u_register_t arg2,
+		u_register_t arg3);
 void bl31_next_el_arch_setup(uint32_t security_state);
 void bl31_set_next_image_type(uint32_t security_state);
 uint32_t bl31_get_next_image_type(void);