dts: mspi: Align op-mode binding with mspi.h enum

enum mspi_op_mode in mspi.h has different syntax to this binding.
Aligning these will allow for cleaner code in the implmented drivers.

Signed-off-by: David Jewsbury <david.jewsbury@nordicsemi.no>
diff --git a/dts/bindings/mspi/mspi-controller.yaml b/dts/bindings/mspi/mspi-controller.yaml
index 6f22d0d..dd7c99e 100644
--- a/dts/bindings/mspi/mspi-controller.yaml
+++ b/dts/bindings/mspi/mspi-controller.yaml
@@ -22,8 +22,8 @@
   op-mode:
     type: string
     enum:
-      - "MSPI_CONTROLLER"
-      - "MSPI_PERIPHERAL"
+      - "MSPI_OP_MODE_CONTROLLER"
+      - "MSPI_OP_MODE_PERIPHERAL"
     description: |
       Indicate MSPI controller or peripheral mode of the controller.
       The controller driver may use this during initialization.