ARM: stm32: Add both PDK2 and DRC02 DT into DHCOM fitImage its

Include both PDK2 and DRC02 DTs in the DHCOM fitImage .its and implement
support in SPL to select the correct configuration entry for U-Boot by
using the machine compatible string from SPL DT.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Patrice Chotard <patrice.chotard@st.com>
Cc: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@st.com>