mips: ath79: Use AR933X_PLL_SWITCH_CLOCK_CONTROL_REG macro define

Add AR933X_PLL_SWITCH_CLOCK_CONTROL_REG define for ar933x chip.

Signed-off-by: Wills Wang <wills.wang@live.com>
diff --git a/arch/mips/mach-ath79/include/mach/ar71xx_regs.h b/arch/mips/mach-ath79/include/mach/ar71xx_regs.h
index dabcad0..7b48524 100644
--- a/arch/mips/mach-ath79/include/mach/ar71xx_regs.h
+++ b/arch/mips/mach-ath79/include/mach/ar71xx_regs.h
@@ -331,6 +331,7 @@
 #define AR933X_PLL_CPU_CONFIG_REG			0x00
 #define AR933X_PLL_CLK_CTRL_REG				0x08
 #define AR933X_PLL_DITHER_FRAC_REG			0x10
+#define AR933X_PLL_SWITCH_CLOCK_CONTROL_REG		0x24
 
 #define AR933X_PLL_CPU_CONFIG_NINT_SHIFT		10
 #define AR933X_PLL_CPU_CONFIG_NINT_MASK			0x3f