imx: imx-common: power down lcdif before boot os

Need to call lcdif_power_down to make lcdif in initial state
before kernel boot. Similar issue for uboot reset with lcdif
enabled, system will hang after serveral times resetting. Need
to let lcdif initial state to make all go well.

Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Eric Nelson <eric.nelson@boundarydevices.com>
Cc: Nikita Kiryanov <nikita@compulab.co.il>
Cc: Tim Harvey <tharvey@gateworks.com>
Cc: Fabio Estevam <fabio.estevam@freescale.com>

arch/arm/imx-common/cpu.c

@@ -279,6 +279,9 @@ void arch_preboot_os(void)
 	/* disable video before launching O/S */
 	ipuv3_fb_shutdown();
 #endif
+#if defined(CONFIG_VIDEO_MXS)
+	lcdif_power_down();
+#endif
 }
 
 void set_chipselect_size(int const cs_size)