imx: mx6: ddr init MMDC according to ddr_type

To i.MX6, DDR3 and LPDDR2 is supported, so rename function mx6_dram_cfg
to mx6_ddr3_cfg and the original mx6_dram_cfg function only is a wrapper.
The new reimplemented function mx6_dram_cfg only invokes mx6_ddr3_cfg
when ddr_type is for DDR3. Later we can use ddr_type to initialize
MMDC for LPDDR2.

Initialize ddr_type for different boards which enable SPL.

Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Tim Harvey <tharvey@gateworks.com>
Cc: Stefan Roese <sr@denx.de>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/arch/arm/include/asm/arch-mx6/mx6-ddr.h b/arch/arm/include/asm/arch-mx6/mx6-ddr.h
index 806fafb..36fcb2b 100644
--- a/arch/arm/include/asm/arch-mx6/mx6-ddr.h
+++ b/arch/arm/include/asm/arch-mx6/mx6-ddr.h
@@ -444,7 +444,7 @@
 /* configure mx6 mmdc registers */
 void mx6_dram_cfg(const struct mx6_ddr_sysinfo *,
 		  const struct mx6_mmdc_calibration *,
-		  const struct mx6_ddr3_cfg *);
+		  const void *);
 
 #endif /* CONFIG_SPL_BUILD */