ARM: rmobile: Stop using rcar-common/common.c on Gen3

Since the Gen3 clock driver now has a .remove callback, it is no
longer necessary to shut the clock down before booting Linux in the
arch_preboot_os hook. Stop using it and while doing so, remove all
the ad-hoc config options which this hook used.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
diff --git a/board/renesas/ulcb/Makefile b/board/renesas/ulcb/Makefile
index 6fe0b48..406fdc8 100644
--- a/board/renesas/ulcb/Makefile
+++ b/board/renesas/ulcb/Makefile
@@ -6,4 +6,4 @@
 # SPDX-License-Identifier: GPL-2.0+
 #
 
-obj-y	:= ulcb.o cpld.o ../rcar-common/common.o
+obj-y	:= ulcb.o cpld.o