ARM: debug-imx: only define DEBUG_IMX_UART_PORT if needed

If debugging on i.MX is enabled DEBUG_IMX_UART_PORT defines which UART
is used for the debug output. If however debugging is off don't only
hide the then unused config item but drop it completely by using a
dependency instead of a conditional prompt.

This fixes DEBUG_IMX_UART_PORT being present in the kernel config even
if DEBUG_LL is disabled.

Signed-off-by: Uwe Kleine-König <[e-mail]>
Signed-off-by: Shawn Guo <[e-mail]>

arch/arm/Kconfig.debug

···
 	depends on ARCH_OMAP2PLUS
 
 config DEBUG_IMX_UART_PORT
-	int "i.MX Debug UART Port Selection" if DEBUG_IMX1_UART || \
-						DEBUG_IMX25_UART || \
-						DEBUG_IMX21_IMX27_UART || \
-						DEBUG_IMX31_UART || \
-						DEBUG_IMX35_UART || \
-						DEBUG_IMX50_UART || \
-						DEBUG_IMX51_UART || \
-						DEBUG_IMX53_UART || \
-						DEBUG_IMX6Q_UART || \
-						DEBUG_IMX6SL_UART || \
-						DEBUG_IMX6SX_UART || \
-						DEBUG_IMX6UL_UART || \
-						DEBUG_IMX7D_UART
+	int "i.MX Debug UART Port Selection"
+	depends on DEBUG_IMX1_UART || \
+		   DEBUG_IMX25_UART || \
+		   DEBUG_IMX21_IMX27_UART || \
+		   DEBUG_IMX31_UART || \
+		   DEBUG_IMX35_UART || \
+		   DEBUG_IMX50_UART || \
+		   DEBUG_IMX51_UART || \
+		   DEBUG_IMX53_UART || \
+		   DEBUG_IMX6Q_UART || \
+		   DEBUG_IMX6SL_UART || \
+		   DEBUG_IMX6SX_UART || \
+		   DEBUG_IMX6UL_UART || \
+		   DEBUG_IMX7D_UART
 	default 1
-	depends on ARCH_MXC
 	help
 	  Choose UART port on which kernel low-level debug messages
 	  should be output.