armv8/ls2080a: configure PMU's PCTBENR to enable WDT

The SP805-WDT module on LS2080A requires configuration of PMU's
PCTBENR register to enable watchdog counter decrement and reset
signal generation. The watchdog clock needs to be enabled first.

Signed-off-by: Yunhui Cui <yunhui.cui@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>
diff --git a/arch/arm/include/asm/arch-fsl-layerscape/immap_lsch3.h b/arch/arm/include/asm/arch-fsl-layerscape/immap_lsch3.h
index 65b3357..c6b9f13 100644
--- a/arch/arm/include/asm/arch-fsl-layerscape/immap_lsch3.h
+++ b/arch/arm/include/asm/arch-fsl-layerscape/immap_lsch3.h
@@ -26,6 +26,7 @@
 #define CONFIG_SYS_FSL_TIMER_ADDR		0x023d0000
 #define CONFIG_SYS_FSL_PMU_CLTBENR		(CONFIG_SYS_FSL_PMU_ADDR + \
 						 0x18A0)
+#define FSL_PMU_PCTBENR_OFFSET (CONFIG_SYS_FSL_PMU_ADDR + 0x8A0)
 
 #define CONFIG_SYS_FSL_WRIOP1_ADDR		(CONFIG_SYS_IMMR + 0x7B80000)
 #define CONFIG_SYS_FSL_WRIOP1_MDIO1	(CONFIG_SYS_FSL_WRIOP1_ADDR + 0x16000)