ARM: rmobile: Repair TMU clock on Gen2

The CPfi/4 is derived from XTAL clock and is not fixed. Undo
the previous commit 7984ac8d1635aebd11175c96b07f937a39f0384d.
Signed-off-by: NMarek Vasut <marek.vasut+renesas@gmail.com>

include/configs/rcar-gen2-common.h

@@ -60,6 +60,6 @@
 #define CONFIG_TMU_TIMER
 #define CONFIG_SYS_TIMER_COUNTS_DOWN
 #define CONFIG_SYS_TIMER_COUNTER	(TMU_BASE + 0xc)	/* TCNT0 */
-#define CONFIG_SYS_TIMER_RATE		(32500000 / 4)		/* CP/4 */
+#define CONFIG_SYS_TIMER_RATE		(CONFIG_SYS_CLK_FREQ / 8)
 
 #endif	/* __RCAR_GEN2_COMMON_H */