pico-imx7d: Correct uart clock root

Correct uart clock root ID. Incorrect ID may result the
clock is gated because rate value 0 is returned in
imx_get_uartclk()

The ID can be ignored if CONFIG_SKIP_LOWLEVEL_INIT is not enabled
because init_clk_uart() will enable all uart clocks in that case.

Signed-off-by: Jun Nie <jun.nie@linaro.org>
diff --git a/arch/arm/include/asm/arch-mx7/clock.h b/arch/arm/include/asm/arch-mx7/clock.h
index f56564e..1d07fde 100644
--- a/arch/arm/include/asm/arch-mx7/clock.h
+++ b/arch/arm/include/asm/arch-mx7/clock.h
@@ -175,6 +175,24 @@
 	CLK_ROOT_MAX,
 };
 
+#if (CONFIG_CONS_INDEX == 0)
+#define UART_CLK_ROOT UART1_CLK_ROOT
+#elif (CONFIG_CONS_INDEX == 1)
+#define UART_CLK_ROOT UART2_CLK_ROOT
+#elif (CONFIG_CONS_INDEX == 2)
+#define UART_CLK_ROOT UART3_CLK_ROOT
+#elif (CONFIG_CONS_INDEX == 3)
+#define UART_CLK_ROOT UART4_CLK_ROOT
+#elif (CONFIG_CONS_INDEX == 4)
+#define UART_CLK_ROOT UART5_CLK_ROOT
+#elif (CONFIG_CONS_INDEX == 5)
+#define UART_CLK_ROOT UART6_CLK_ROOT
+#elif (CONFIG_CONS_INDEX == 6)
+#define UART_CLK_ROOT UART7_CLK_ROOT
+#else
+#error "Invalid IMX UART ID for serial console is defined"
+#endif
+
 struct clk_root_setting {
 	enum clk_root_index root;
 	u32 setting;
diff --git a/arch/arm/mach-imx/mx7/clock.c b/arch/arm/mach-imx/mx7/clock.c
index 8cda71c..e364b16 100644
--- a/arch/arm/mach-imx/mx7/clock.c
+++ b/arch/arm/mach-imx/mx7/clock.c
@@ -53,7 +53,7 @@
 
 u32 imx_get_uartclk(void)
 {
-	return get_root_clk(UART1_CLK_ROOT);
+	return get_root_clk(UART_CLK_ROOT);
 }
 
 u32 imx_get_fecclk(void)