ARM: dts: stm32: Don't probe red led at boot for stm32mp157a-dk1-u-boot

ARM: dts: stm32: Don't probe red led at boot for stm32mp157a-dk1-u-boot

red led and button dedicated to fastboot share the same gpio GPIOA13.
Led driver is probed early so the corresponding gpio is taken and
configured in output which forbid fastboot and stm32prog button usage.

To avoid this, remove the "default-state" property from red led node.

This will avoid to trigger the led driver probe() to configure the led
default state during startup.

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