mx5/clock: fix clear bit fields issue in _clk_ccgr_disable function

We can see MXC_CCM_CCGRx_MOD_OFF is defined as 0 while
MXC_CCM_CCGRx_CG_MASK is defined as 0x3 in crm_regs.h, here in the
_clk_ccgr_disable function, we want to clear the corresponding enable
bit fields to disable this clock, so we should choose MASK instead of
OFF otherwise clocks can't be disabled.

Signed-off-by: Jason Wang <jason77.wang@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

arch/arm/mach-mx5/clock-mx51.c

@@ -56,7 +56,7 @@ static void _clk_ccgr_disable(struct clk *clk)
 {
 	u32 reg;
 	reg = __raw_readl(clk->enable_reg);
-	reg &= ~(MXC_CCM_CCGRx_MOD_OFF << clk->enable_shift);
+	reg &= ~(MXC_CCM_CCGRx_CG_MASK << clk->enable_shift);
 	__raw_writel(reg, clk->enable_reg);
 
 }