configs: stm32: introduce stm32mp15-odyssey_defconfig

configs: stm32: introduce stm32mp15-odyssey_defconfig

U-Boot DT for stm32mp157c-odyssey is richer than the kernel DT one.
None of the stm32mp157c-odyssey's contributors answered to my request
to update kernel DT and i didn't have this board to test.
The simpler is to add a dedicated stm32mp15-odyssey_defconfig with
OF_UPSTREAM flag unset.

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>