spi: dt-bindings: stm32: deprecate st,spi-midi-ns property

The vendor `st,spi-midi-ns` property is no longer needed and
has been deprecated in favor of a generic solution.

Signed-off-by: Clément Le Goffic <clement.legoffic@foss.st.com>
Link: https://patch.msgid.link/20250616-spi-upstream-v1-6-7e8593f3f75d@foss.st.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: clegoffic

Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml

@@ -115,6 +115,7 @@ properties:
     maxItems: 4
 
   st,spi-midi-ns:
+    deprecated: true
     description: |
       Only for STM32H7, (Master Inter-Data Idleness) minimum time
       delay in nanoseconds inserted between two consecutive data frames.