MX51EVK: UART does not print out the early information

The early bootup information is not print out due to
the UART pin iomux not set up correctly before board_init

Add the board_early_init_f function and enable the
CONFIG_BOARD_EARLY_INIT_F. Move the UART pin setting
from board_init to board_early_init_f function.

This patch also move the FEC pin iomux setup to the
board_early_init_f.

Signed-off-by: Jason Liu <r64343@freescale.com>
diff --git a/board/freescale/mx51evk/mx51evk.c b/board/freescale/mx51evk/mx51evk.c
index 2160d5a..7c50c54 100644
--- a/board/freescale/mx51evk/mx51evk.c
+++ b/board/freescale/mx51evk/mx51evk.c
@@ -399,6 +399,14 @@
 }
 #endif
 
+int board_early_init_f(void)
+{
+	setup_iomux_uart();
+	setup_iomux_fec();
+
+	return 0;
+}
+
 int board_init(void)
 {
 	system_rev = get_cpu_rev();
@@ -407,9 +415,6 @@
 	/* address of boot parameters */
 	gd->bd->bi_boot_params = PHYS_SDRAM_1 + 0x100;
 
-	setup_iomux_uart();
-	setup_iomux_fec();
-
 	return 0;
 }