fix(errata): workaround for Cortex-A710 erratum 2058056

Cortex-A710 erratum 2058056 is a Cat B erratum that applies to
revisions r0p0, r1p0, and r2p0. It is still open. The workaround
is to write the value 4'b1001 to the PF_MODE bits in the
IMP_CPUECTLR2_EL1 register which will place the data prefetcher
in the most conservative mode instead of disabling it.

SDEN can be found here:
https://developer.arm.com/documentation/SDEN1775101/latest

Signed-off-by: nayanpatel-arm <nayankumar.patel@arm.com>
Change-Id: I7ce5181b3b469fbbb16501e633116e119b8bf4f1
diff --git a/docs/design/cpu-specific-build-macros.rst b/docs/design/cpu-specific-build-macros.rst
index 80e7821..362f19d 100644
--- a/docs/design/cpu-specific-build-macros.rst
+++ b/docs/design/cpu-specific-build-macros.rst
@@ -393,6 +393,10 @@
    Cortex-A710 CPU. This needs to be enabled for revision r2p0 of the CPU and
    is still open.
 
+-  ``ERRATA_A710_2058056``: This applies errata 2058056 workaround to
+   Cortex-A710 CPU. This needs to be enabled for revisions r0p0, r1p0 and r2p0
+   of the CPU and is still open.
+
 For Neoverse N2, the following errata build flags are defined :
 
 -  ``ERRATA_N2_2067956``: This applies errata 2067956 workaround to Neoverse-N2