dm: migrate the dm_warn to use the log macro
Migrate the dm_warn function to log macro with
LOGC_DM category and LOGL_WARNING level.
This macro allows filtering with log command and allows
output on all log backend.
Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>