arm: rmobile: rcar: Move arch_preboot_os function to rcar-gen2-common/common.c

The arch_preboot_os function used in boards using R-Car ARM SoC (r8a7790,
r8a7791, r8a7793 and r8a7794) is common.
This makes rcar-gen2-common/common.c file providing common function for
R-Car ARM SoC, and moves this function to this file.

Signed-off-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>
Signed-off-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>
diff --git a/board/renesas/gose/Makefile b/board/renesas/gose/Makefile
index a4fb6cc..2dac748 100644
--- a/board/renesas/gose/Makefile
+++ b/board/renesas/gose/Makefile
@@ -6,4 +6,4 @@
 # SPDX-License-Identifier: GPL-2.0
 #
 
-obj-y	:= gose.o qos.o
+obj-y	:= gose.o qos.o ../rcar-gen2-common/common.o
diff --git a/board/renesas/gose/gose.c b/board/renesas/gose/gose.c
index 0b2d904..677b976 100644
--- a/board/renesas/gose/gose.c
+++ b/board/renesas/gose/gose.c
@@ -60,16 +60,6 @@
 	return 0;
 }
 
-#define TSTR0		0x04
-#define TSTR0_STR0	0x01
-void arch_preboot_os(void)
-{
-	/* stop TMU0 */
-	mstp_clrbits_le32(TMU_BASE + TSTR0, TMU_BASE + TSTR0, TSTR0_STR0);
-	/* Disable TMU0 */
-	mstp_setbits_le32(MSTPSR1, SMSTPCR1, TMU0_MSTP125);
-}
-
 #define PUPR5		0xE6060114
 #define PUPR5_ETH	0x3FFC0000
 #define PUPR5_ETH_MAGIC	(1 << 27)