mtd: nand: mxs_nand_spl: Fix to remove twise 'NAND' print

SPL from nand will print 'NAND' in boot_from_devices based on
the image_loader name, remove the extra 'NAND ' in mxs_nand_spl driver.

Original behaviour:
-------------------
U-Boot SPL 2017.01-rc2-gf84dd8b (Jan 02 2017 - 22:24:19)
Trying to boot from NANDNAND : 512 MiB

After the fix:
-------------
U-Boot SPL 2017.01-rc2-gf84dd8b-dirty (Jan 02 2017 - 23:17:00)
Trying to boot from NAND: 512 MiB

Cc: Tom Rini <trini@konsulko.com>
Signed-off-by: Jagan Teki <jagan@openedev.com>

drivers/mtd/nand/mxs_nand_spl.c

@@ -153,7 +153,7 @@ static int mxs_nand_init(void)
 	nand_chip.numchips = 1;
 
 	/* identify flash device */
-	puts("NAND : ");
+	puts(": ");
 	if (mxs_flash_ident(mtd)) {
 		printf("Failed to identify\n");
 		return -1;