Workaround for Cortex A76 erratum 1800710

Cortex A76 erratum 1800710 is a Cat B erratum, present in older
revisions of the Cortex A76 processor core.  The workaround is to
set a bit in the ECTLR_EL1 system register, which disables allocation
of splintered pages in the L2 TLB.

This errata is explained in this SDEN:
https://static.docs.arm.com/sden885749/g/Arm_Cortex_A76_MP052_Software_Developer_Errata_Notice_v20.pdf

Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: Ifc34f2e9e053dcee6a108cfb7df7ff7f497c9493
diff --git a/docs/design/cpu-specific-build-macros.rst b/docs/design/cpu-specific-build-macros.rst
index 53da688..264d0c6 100644
--- a/docs/design/cpu-specific-build-macros.rst
+++ b/docs/design/cpu-specific-build-macros.rst
@@ -230,6 +230,9 @@
 -  ``ERRATA_A76_1791580``: This applies errata 1791580 workaround to Cortex-A76
    CPU. This needs to be enabled only for revision <= r4p0 of the CPU.
 
+-  ``ERRATA_A76_1800710``: This applies errata 1800710 workaround to Cortex-A76
+   CPU. This needs to be enabled only for revision <= r4p0 of the CPU.
+
 For Cortex-A78, the following errata build flags are defined :
 
 -  ``ERRATA_A78_1688305``: This applies errata 1688305 workaround to Cortex-A78