ARM: dts: stm32: set the DCMI pins on stm32mp157c-odyssey

The Seeed Odyssey-STM32MP157C board has a 20-pin DVP camera output. The
DCMI pins used on this output are defined in the pin state definition
&pinctrl/dcmi-1, AKA &dcmi_pins_b (added in mainline commit
02814a41). Set these pins as the default
pinctrl of the DCMI peripheral in the board device tree.

The pins are not used for any other purpose, so it seems safe to assume
most users will not need to override (delete) what this patch provides.
status defaults to "disabled", so the peripheral will not be
unnecessarily started. And the users who actually intend to make use of
a camera on the DVP port will have this little part of the configuration
ready.

Signed-off-by: Grzegorz Szymaszek <gszymaszek@short.pl>
Reviewed-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>