Update ST7789 SPI driver to use ndarray.ndim

See v923z/micropython-ulab#725

Author: sfe-SparkFro

drivers/display/st7789_spi.py

@@ -264,7 +264,7 @@ def _get_common_roi_with_buffer(self, image):
 
         # Determing number of rows and columns in the image
         image_rows = image.shape[0]
-        if len(image.shape) < 2:
+        if image.ndim < 2:
             image_cols = 1
         else:
             image_cols = image.shape[1]
@@ -314,7 +314,7 @@ def _write_image_to_buffer_bgr565(self, image_roi, buffer_roi):
             buffer_roi (ndarray): Buffer region of interest
         """
         # Determine the number of channels in the image
-        if len(image_roi.shape) < 3:
+        if image_roi.ndim < 3:
             ch = 1
         else:
             ch = image_roi.shape[2]