Cortex-A55: Implement workaround for erratum 778703

Change-Id: I094e5cb2c44618e7a4116af5fbb6b18078a79951
Signed-off-by: Ambroise Vincent <ambroise.vincent@arm.com>
diff --git a/docs/cpu-specific-build-macros.rst b/docs/cpu-specific-build-macros.rst
index 897c771..77e12d1 100644
--- a/docs/cpu-specific-build-macros.rst
+++ b/docs/cpu-specific-build-macros.rst
@@ -102,6 +102,9 @@
 -  ``ERRATA_A55_768277``: This applies errata 768277 workaround to Cortex-A55
    CPU. This needs to be enabled only for revision r0p0 of the CPU.
 
+-  ``ERRATA_A55_778703``: This applies errata 778703 workaround to Cortex-A55
+   CPU. This needs to be enabled only for revision r0p0 of the CPU.
+
 For Cortex-A57, the following errata build flags are defined :
 
 -  ``ERRATA_A57_806969``: This applies errata 806969 workaround to Cortex-A57