am33xx: Stop using PHYS_DRAM_1 define

We defined PHYS_DRAM_1 to 0x80000000 (start of DRAM) and then used this
for CONFIG_SYS_SDRAM_BASE.  But then we kept on referencing PHYS_DRAM_1
in other places.  Change to directly setting CONFIG_SYS_DRAM_BASE and
then using that name in code.

Signed-off-by: Tom Rini <trini@ti.com>
diff --git a/board/ti/ti814x/evm.c b/board/ti/ti814x/evm.c
index 31ddc68..e406326 100644
--- a/board/ti/ti814x/evm.c
+++ b/board/ti/ti814x/evm.c
@@ -112,7 +112,7 @@
  */
 int board_init(void)
 {
-	gd->bd->bi_boot_params = PHYS_DRAM_1 + 0x100;
+	gd->bd->bi_boot_params = CONFIG_SYS_SDRAM_BASE + 0x100;
 	return 0;
 }