doc: phytec: k3: Add a common part for Environment and EFI Capsules

Provide a common part for our K3 based boards including general details
about environment handling and EFI capsule updates.

Signed-off-by: Wadim Egorov <w.egorov@phytec.de>
diff --git a/doc/board/phytec/phycore-am62x.rst b/doc/board/phytec/phycore-am62x.rst
index 56c1fd8..36315b4 100644
--- a/doc/board/phytec/phycore-am62x.rst
+++ b/doc/board/phytec/phycore-am62x.rst
@@ -176,6 +176,8 @@
      - 11001010
      - 00100000
 
+.. include:: k3-common.rst
+
 Further Information
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