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/am335x/board.c b/board/ti/am335x/board.c
index eac9cc9..04c37e2 100644
--- a/board/ti/am335x/board.c
+++ b/board/ti/am335x/board.c
@@ -343,7 +343,7 @@
 		STNOR_GPMC_CONFIG5, STNOR_GPMC_CONFIG6, STNOR_GPMC_CONFIG7 };
 #endif
 
-	gd->bd->bi_boot_params = PHYS_DRAM_1 + 0x100;
+	gd->bd->bi_boot_params = CONFIG_SYS_SDRAM_BASE + 0x100;
 
 	gpmc_init();