mx6qsabreauto: Avoid hardcoded RAM size

Instead of passing the total RAM size via PHYS_SDRAM_SIZE option,
we should better use imx_ddr_size() function, which automatically
determines the RAM size.

Signed-off-by: Vanessa Maegima <vanessa.maegima@nxp.com>
Acked-by: Fabio Estevam <fabio.estevam@nxp.com>

board/freescale/mx6qsabreauto/mx6qsabreauto.c

@@ -64,7 +64,7 @@ DECLARE_GLOBAL_DATA_PTR;
 
 int dram_init(void)
 {
-	gd->ram_size = get_ram_size((void *)PHYS_SDRAM, PHYS_SDRAM_SIZE);
+	gd->ram_size = imx_ddr_size();
 
 	return 0;
 }