ARM: dts: stm32: Split AV96 into DHCOR SoM and AV96 board

The AV96 is in fact an assembly of DH Electronics DHCOR SoM on top
of an AV96 reference board. Split the DTs to reflect that and make
sure to DHCOR SoM can be reused on other boards easily.

It is also highly recommended to configure the board for the DHCOM
make stm32mp15_dhcom_basic_defconfig
make DEVICE_TREE=stm32mp15xx-dhcor-avenger96
as that permits reusing the board code for the DH components, like
accessing and reading out the ethernet MAC from EEPROM.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: Patrick Delaunay <patrick.delaunay@st.com>
Cc: Patrice Chotard <patrice.chotard@st.com>
Change-Id: I7db47280d4eb0d668eb4e006355240271154f97f
diff --git a/doc/board/st/stm32mp1.rst b/doc/board/st/stm32mp1.rst
index b7a0fbf..b3856be 100644
--- a/doc/board/st/stm32mp1.rst
+++ b/doc/board/st/stm32mp1.rst
@@ -51,11 +51,11 @@
 
 Currently the following boards are supported:
 
- + stm32mp157a-avenger96.dts
  + stm32mp157a-dk1.dts
  + stm32mp157c-dk2.dts
  + stm32mp157c-ed1.dts
  + stm32mp157c-ev1.dts
+ + stm32mp15xx-dhcor-avenger96.dts
 
 Boot Sequences
 --------------
@@ -153,9 +153,9 @@
 
    + stm32mp157c-dk2
 
-+ avenger96: Avenger96 board from Arrow Electronics
++ avenger96: Avenger96 board from Arrow Electronics based on DH Elec. DHCOR SoM
 
-   + stm32mp157a-avenger96
+   + stm32mp15xx-dhcor-avenger96
 
 Build Procedure
 ---------------
@@ -237,7 +237,7 @@
 
      # export KBUILD_OUTPUT=stm32mp15_basic
      # make stm32mp15_basic_defconfig
-     # make DEVICE_TREE=stm32mp157a-avenger96 all
+     # make DEVICE_TREE=stm32mp15xx-dhcor-avenger96 all
 
 6. Output files