plat: marvell: armada: a3k: Add new compile option A3720_DB_PM_WAKEUP_SRC

This new compile option is only for Armada 3720 Development Board. When
it is set to 1 then TF-A will setup PM wake up src configuration.

By default this new option is disabled as it is board specific and no
other A37xx board has PM wake up src configuration.

Currently neither upstream U-Boot nor upstream Linux kernel has wakeup
support for A37xx platforms, so having it disabled does not cause any
issue.

Prior this commit PM wake up src configuration specific for Armada 3720
Development Board was enabled for every A37xx board. After this change it
is enabled only when compiling with build flag A3720_DB_PM_WAKEUP_SRC=1

Signed-off-by: Pali Rohár <pali@kernel.org>
Change-Id: I09fea1172c532df639acb3bb009cfde32d3c5766
diff --git a/docs/plat/marvell/armada/build.rst b/docs/plat/marvell/armada/build.rst
index c74ff7a..c9f5e82 100644
--- a/docs/plat/marvell/armada/build.rst
+++ b/docs/plat/marvell/armada/build.rst
@@ -112,6 +112,11 @@
         This option is needed on Turris MOX as a workaround to a HW bug which causes reset to
         sometime hang the board.
 
+- A3720_DB_PM_WAKEUP_SRC
+
+        For Armada 3720 Develpment Board only, when ``A3720_DB_PM_WAKEUP_SRC=1``,
+        TF-A will setup PM wake up src configuration. This option is disabled by default.
+
 - MARVELL_SECURE_BOOT
 
         Build trusted(=1)/non trusted(=0) image, default is non trusted.