board: ti: am64x: Switch to standard boot flow

Switch to using bootstd. Note with this change, we will stop using
distro_bootcmd and instead depend entirely on bootflow method of
starting the system up.

Drop header files that are no longer needed in am64x_evm.h.
k3_dfu.h is available via k3_dfu.env in am64x.env.

Drop unused macro CFG_SYS_SDRAM_BASE1.

Signed-off-by: Roger Quadros <rogerq@kernel.org>
Reviewed-by: Nishanth Menon <nm@ti.com>
diff --git a/board/ti/am64x/am64x.env b/board/ti/am64x/am64x.env
index 68e4222..efd736b 100644
--- a/board/ti/am64x/am64x.env
+++ b/board/ti/am64x/am64x.env
@@ -15,6 +15,7 @@
 args_all=setenv optargs earlycon=ns16550a,mmio32,0x02800000 ${mtdparts}
 run_kern=booti ${loadaddr} ${rd_spec} ${fdtaddr}
 
+boot_targets=mmc1 mmc0 usb pxe dhcp
 boot=mmc
 mmcdev=1
 bootpart=1:2