mxs: spl_mem_init: Fix comment about start bit

Start bit is part of HW_DRAM_CTL8 register, so  fix the comment.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>

arch/arm/cpu/arm926ejs/mxs/spl_mem_init.c

@@ -267,7 +267,7 @@ static void mx23_mem_init(void)
 
 	initialize_dram_values();
 
-	/* Set START bit in DRAM_CTL16 */
+	/* Set START bit in DRAM_CTL8 */
 	setbits_le32(MXS_DRAM_BASE + 0x20, 1 << 16);
 
 	clrbits_le32(MXS_DRAM_BASE + 0x40, 1 << 17);