board: ti: k3: Remove need for CFG_SYS_SDRAM_BASE

The base address of extended DDR does not change across the K3 family.
Setting this per SoC is not needed. Remove this definition to help
remove the last bits from K3 include/configs/*.h files.

Signed-off-by: Andrew Davis <afd@ti.com>
diff --git a/board/ti/am65x/evm.c b/board/ti/am65x/evm.c
index 975eb17..df20902 100644
--- a/board/ti/am65x/evm.c
+++ b/board/ti/am65x/evm.c
@@ -73,13 +73,13 @@
 int dram_init_banksize(void)
 {
 	/* Bank 0 declares the memory available in the DDR low region */
-	gd->bd->bi_dram[0].start = CFG_SYS_SDRAM_BASE;
+	gd->bd->bi_dram[0].start = 0x80000000;
 	gd->bd->bi_dram[0].size = 0x80000000;
 	gd->ram_size = 0x80000000;
 
 #ifdef CONFIG_PHYS_64BIT
 	/* Bank 1 declares the memory available in the DDR high region */
-	gd->bd->bi_dram[1].start = CFG_SYS_SDRAM_BASE1;
+	gd->bd->bi_dram[1].start = 0x880000000;
 	gd->bd->bi_dram[1].size = 0x80000000;
 	gd->ram_size = 0x100000000;
 #endif