dt-bindings: arm: stm32: correct blank lines

Correct blank lines to precesily separate entries.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>

Documentation/devicetree/bindings/arm/stm32/stm32.yaml

@@ -64,8 +64,8 @@ properties:
               - st,stm32mp157c-ed1
               - st,stm32mp157a-dk1
               - st,stm32mp157c-dk2
-
           - const: st,stm32mp157
+
       - items:
           - const: st,stm32mp157c-ev1
           - const: st,stm32mp157c-ed1
@@ -110,6 +110,7 @@ properties:
           - const: oct,stm32mp15xx-osd32
           - enum:
               - st,stm32mp157
+
       - description: Odyssey STM32MP1 SoM based Boards
         items:
           - enum: