Platform: Add support for BL5340 DVK

This adds supports for the Laird Connectivity BL5340 DVK (development kit)
application core, which is based on the nRF5340 SoC.

Signed-off-by: Jamie McCrae <jamie.mccrae@lairdconnect.com>
Change-Id: I062412918d4cbe692748c1a31fef444190f50661
diff --git a/docs/technical_references/tfm_secure_boot.rst b/docs/technical_references/tfm_secure_boot.rst
index 36ea036..528e7b7 100644
--- a/docs/technical_references/tfm_secure_boot.rst
+++ b/docs/technical_references/tfm_secure_boot.rst
@@ -256,6 +256,8 @@
 +---------------------+-----------------+---------------+----------+----------------+--------------+
 | nRF5340 DK          | Yes             | Yes           | No       | No             | No           |
 +---------------------+-----------------+---------------+----------+----------------+--------------+
+| BL5340 DVK          | Yes             | Yes           | Yes      | No             | No           |
++---------------------+-----------------+---------------+----------+----------------+--------------+
 
 .. [1] To disable BL2, please set the ``BL2`` cmake option to ``OFF``