ARM: imx6: Rename DEBUG_IMX6Q_UART to UART4

Different boards may use differenct UART ports for debugging.
To be able to add different debug UART configurations (e.g. UART2),
rename the existing general DEBUG_IMX6Q_UART to DEBUG_IMX6Q_UART4.

Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/arch/arm/mach-imx/lluart.c b/arch/arm/mach-imx/lluart.c
index d4ab6f2..0213f8d 100644
--- a/arch/arm/mach-imx/lluart.c
+++ b/arch/arm/mach-imx/lluart.c
@@ -17,7 +17,7 @@
 #include <mach/hardware.h>
 
 static struct map_desc imx_lluart_desc = {
-#ifdef CONFIG_DEBUG_IMX6Q_UART
+#ifdef CONFIG_DEBUG_IMX6Q_UART4
 	.virtual	= MX6Q_IO_P2V(MX6Q_UART4_BASE_ADDR),
 	.pfn		= __phys_to_pfn(MX6Q_UART4_BASE_ADDR),
 	.length		= MX6Q_UART4_SIZE,