hexagon: partial im2col support (#26007)

* hexagon: add IM2COL op

Add Hexagon IM2COL support targeting only patch-embedding convolutions.

* hexagon: im2col refactor and cleanup

* hex-im2col: instrument and update im2col.

* hex-im2col: add local htp_vtcm_layout computation.

ggml/src/ggml-hexagon/htp/main.c

@@ -781,6 +781,9 @@ static int execute_op(struct htp_ops_context * octx) {
         case HTP_OP_PAD:
             return op_pad(octx);
 
+        case HTP_OP_IM2COL:
+            return op_im2col(octx);
+
         case HTP_OP_CONCAT:
             return op_concat(octx);