ARM: imx: fix typo "DEBUG_IMX50_IMX53_UART"

Commit f8c95fe (ARM: imx: support DEBUG_LL uart port selection for all
i.MX SoCs) had a typo that DEBUG_IMX50_IMX53_UART should be
DEBUG_IMX53_UART.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
index acdddda..ecfcdba 100644
--- a/arch/arm/Kconfig.debug
+++ b/arch/arm/Kconfig.debug
@@ -492,7 +492,7 @@
 						DEBUG_IMX31_UART || \
 						DEBUG_IMX35_UART || \
 						DEBUG_IMX51_UART || \
-						DEBUG_IMX50_IMX53_UART || \
+						DEBUG_IMX53_UART || \
 						DEBUG_IMX6Q_UART
 	default 1
 	help