utils: gen-controls: Improve YAML notation for variable-size array controls

Array controls specify the array size through the YAML 'size' element,
which stores a list of values, one per dimension. Variable-size arrays
currently use an empty 'size' list, which prevents describing the number
of dimensions of the array.

Improve this by using the same notation for fixed-size and variable-size
array controls. Dimensions that are not fixed are described as a string
instead of an integer, such as [n], [n,3] or [w,h]. The strings have
currently no special meaning, this may change in the future.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>

src/libcamera/control_ids.yaml

@@ -525,7 +525,7 @@ controls:
         the window where the focal distance for the objects shown in that part
         of the image are closest to the camera.
 
-      size: []
+      size: [n]
 
   - AfTrigger:
       type: int32_t

src/libcamera/property_ids.yaml

@@ -497,7 +497,7 @@ controls:
 
   - PixelArrayOpticalBlackRectangles:
       type: Rectangle
-      size: []
+      size: [n]
       description: |
         The pixel array region(s) which contain optical black pixels
         considered valid for calibration purposes.
@@ -592,7 +592,7 @@ controls:
 
   - PixelArrayActiveAreas:
       type: Rectangle
-      size: []
+      size: [n]
       description: |
         The PixelArrayActiveAreas property defines the (possibly multiple and
         overlapping) portions of the camera sensor readable pixel matrix