feat(context-mgmt): report context memory usage

This patch provides a reporting functionality to display the memory
consumed by the context in each security state and for each exception
level. Flag PLATFORM_REPORT_CTX_MEM_USE enables or disables this
feature.

Change-Id: I1515366bf87561dcedf2b3206be167804df681d4
Signed-off-by: Juan Pablo Conde <juanpablo.conde@arm.com>
Signed-off-by: Jayanth Dodderi Chidanand <jayanthdodderi.chidanand@arm.com>
diff --git a/docs/getting_started/build-options.rst b/docs/getting_started/build-options.rst
index 3d409e3..5b03967 100644
--- a/docs/getting_started/build-options.rst
+++ b/docs/getting_started/build-options.rst
@@ -722,6 +722,11 @@
    platform makefile named ``platform.mk``. For example, to build TF-A for the
    Arm Juno board, select PLAT=juno.
 
+-  ``PLATFORM_REPORT_CTX_MEM_USE``: Reports the context memory allocated for
+   each core as well as the global context. The data includes the memory used
+   by each world and each privileged exception level. This build option is
+   applicable only for ``ARCH=aarch64`` builds. The default value is 0.
+
 -  ``PRELOADED_BL33_BASE``: This option enables booting a preloaded BL33 image
    instead of the normal boot flow. When defined, it must specify the entry
    point address for the preloaded BL33 image. This option is incompatible with