dm: include <dm/util.h> from driver/core/dump.c

Include <dm/util.h> to fix sparse warnings:
symbol 'dm_dump_all' was not declared. Should it be static?
symbol 'dm_dump_uclass' was not declared. Should it be static?

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>