dm: add cells_count parameter in *_count_phandle_with_args

dm: add cells_count parameter in *_count_phandle_with_args

The cell_count argument is required when cells_name is NULL.

This patch adds this parameter in live tree API
- of_count_phandle_with_args
- ofnode_count_phandle_with_args
- dev_count_phandle_with_args

This parameter solves issue when these API is used to count
the number of element of a cell without cell name. This parameter
allow to force the size cell.

For example:
  count = dev_count_phandle_with_args(dev, "array", NULL, 3);

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>