ARM: imx: add initial imx6dl support

The i.MX6 DualLite/Solo is another i.MX6 family SoC, which is highly
compatible with i.MX6 Quad/Dual.  And that's why we choose to support
it using imx6q code with cpu_is_imx6dl() check when necessary.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index 9b31f43..7e911fd 100644
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -234,11 +234,11 @@
 		  on i.MX53.
 
 	config DEBUG_IMX6Q_UART
-		bool "i.MX6Q Debug UART"
+		bool "i.MX6Q/DL Debug UART"
 		depends on SOC_IMX6Q
 		help
 		  Say Y here if you want kernel low-level debugging support
-		  on i.MX6Q.
+		  on i.MX6Q/DL.
 
 	config DEBUG_MMP_UART2
 		bool "Kernel low-level debugging message via MMP UART2"