ARM: imx6q: let users input debug uart port number

imx6q gets 5 uart ports in total.  Different board design may choose
different port as debug uart.  For example, imx6q-sabresd uses UART1,
imx6q-sabrelite uses UART2 and imx6q-arm2 uses UART4.  Rather than
bloating DEBUG_LL choice list with all these uart ports, the patch
introduces DEBUG_IMX6Q_UART_PORT for users to input uart port number
when DEBUG_IMX6Q_UART is selected inside DEBUG_LL choice.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index 5566520..5dc7109 100644
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -209,20 +209,12 @@
 		  Say Y here if you want kernel low-level debugging support
 		  on i.MX50 or i.MX53.
 
-	config DEBUG_IMX6Q_UART2
-		bool "i.MX6Q Debug UART2"
+	config DEBUG_IMX6Q_UART
+		bool "i.MX6Q Debug UART"
 		depends on SOC_IMX6Q
 		help
 		  Say Y here if you want kernel low-level debugging support
-		  on i.MX6Q UART2. This is correct for e.g. the SabreLite
-                  board.
-
-	config DEBUG_IMX6Q_UART4
-		bool "i.MX6Q Debug UART4"
-		depends on SOC_IMX6Q
-		help
-		  Say Y here if you want kernel low-level debugging support
-		  on i.MX6Q UART4.
+		  on i.MX6Q.
 
 	config DEBUG_MMP_UART2
 		bool "Kernel low-level debugging message via MMP UART2"
@@ -409,6 +401,15 @@
 
 endchoice
 
+config DEBUG_IMX6Q_UART_PORT
+	int "i.MX6Q Debug UART Port (1-5)" if DEBUG_IMX6Q_UART
+	range 1 5
+	default 1
+	depends on SOC_IMX6Q
+	help
+	  Choose UART port on which kernel low-level debug messages
+	  should be output.
+
 config DEBUG_LL_INCLUDE
 	string
 	default "debug/icedcc.S" if DEBUG_ICEDCC
@@ -418,8 +419,7 @@
 				 DEBUG_IMX31_IMX35_UART || \
 				 DEBUG_IMX51_UART || \
 				 DEBUG_IMX50_IMX53_UART ||\
-				 DEBUG_IMX6Q_UART2 || \
-				 DEBUG_IMX6Q_UART4
+				 DEBUG_IMX6Q_UART
 	default "debug/highbank.S" if DEBUG_HIGHBANK_UART
 	default "debug/mvebu.S" if DEBUG_MVEBU_UART
 	default "debug/picoxcell.S" if DEBUG_PICOXCELL_UART