drivers: mipi_dbi: allow MIPI mode to be set via devicetree

Enable MIPI mode to be set via devicetree, for displays that support
multiple MIPI DBI modes. This commit also adds new helpers for displays
that allow drivers to initialize the entire MIPI DBI configuration
structure from devicetree

Signed-off-by: Daniel DeGrasse <daniel.degrasse@nxp.com>

dts/bindings/mipi-dbi/mipi-dbi-device.yaml

@@ -11,3 +11,14 @@ properties:
   mipi-max-frequency:
     type: int
     description: Maximum clock frequency of device's MIPI interface in Hz
+
+  mipi-mode:
+    type: int
+    description: |
+      MIPI DBI mode in use. Use the macros not the actual enum value, here is
+      the concordance list (see dt-bindings/mipi_dbi/mipi_dbi.h)
+        1     MIPI_DBI_MODE_SPI_3WIRE
+        2     MIPI_DBI_MODE_SPI_4WIRE
+    enum:
+      - 1
+      - 2