BL2_AT_EL3: 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 |   +44 |   +0  |   +0  |   +0   |
|                            |  0.2% |       |       |        |
+----------------------------+-------+-------+-------+--------+
| ENABLE_PAUTH = 1           |  +712 |   +0  |  +16  |   +0   |
|                            |  3.1% |       |  0.9% |        |
+----------------------------+-------+-------+-------+--------+

The results are valid for the following build configuration:

    make PLAT=fvp SPD=tspd DEBUG=1 \
    BL2_AT_EL3=1                   \
    CTX_INCLUDE_PAUTH_REGS=1       \
    ENABLE_PAUTH=1

Change-Id: I1c0616e7dea30962a92b4fd113428bc30a018320
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/include/bl2/bl2.h b/include/bl2/bl2.h
index b3f9a87..73f5ac7 100644
--- a/include/bl2/bl2.h
+++ b/include/bl2/bl2.h
@@ -11,6 +11,8 @@
 
 void bl2_setup(u_register_t arg0, u_register_t arg1, u_register_t arg2,
 	       u_register_t arg3);
+void bl2_el3_setup(u_register_t arg0, u_register_t arg1, u_register_t arg2,
+		   u_register_t arg3);
 void bl2_main(void);
 
 #endif /* BL2_H */