OMAP4/5: emif: Correct the emif power mgt shadow register bit fields.

PD_TIM bit field which specifies the power down timing is defined
to occupy bits 8-11, where as it is actually from 12-15 bits.
So correcting this.

Signed-off-by: R Sricharan <r.sricharan@ti.com>

arch/arm/include/asm/emif.h

@@ -226,8 +226,8 @@
 #define EMIF_REG_CS_TIM_MASK			(0xf << 0)
 
 /* PWR_MGMT_CTRL_SHDW */
-#define EMIF_REG_PD_TIM_SHDW_SHIFT			8
-#define EMIF_REG_PD_TIM_SHDW_MASK			(0xf << 8)
+#define EMIF_REG_PD_TIM_SHDW_SHIFT			12
+#define EMIF_REG_PD_TIM_SHDW_MASK			(0xf << 12)
 #define EMIF_REG_SR_TIM_SHDW_SHIFT			4
 #define EMIF_REG_SR_TIM_SHDW_MASK			(0xf << 4)
 #define EMIF_REG_CS_TIM_SHDW_SHIFT			0