spi: stm32: disable spi-slave property for stm32f4-f7

STM32F4 and STM32F7 can't switch to spi device mode.
Forbid this property with compatible "st,stm32f4-spi".

Signed-off-by: Alain Volmat <alain.volmat@foss.st.com>
Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>
Link: https://lore.kernel.org/r/20230615075815.310261-4-valentin.caron@foss.st.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: Alain Volmat

Documentation/devicetree/bindings/spi/st,stm32-spi.yaml

@@ -27,6 +27,7 @@ allOf:
     then:
       properties:
         st,spi-midi-ns: false
+        spi-slave: false
 
 properties:
   compatible: