boot: call dhcp_run in pxe bootmethod

A recent change tried to speed up EFI booting by not calling dhcp_run
from eth_bootdev_hunt() every time. PXE so far relied on that dhcp_run
call to get an IP address.

Fix that by adding a dhcp_run call to the pxe bootflow, with autoload
disabled to only get the ip address and nothing else.

Suggested-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Fixes: 1f68057e03 ("net: eth_bootdev_hunt() should not run DHCP")
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

boot/bootmeth_pxe.c

@@ -73,6 +73,10 @@ static int extlinux_pxe_read_bootflow(struct udevice *dev,
 		return log_msg_ret("pxeb", -EPERM);
 	addr = simple_strtoul(addr_str, NULL, 16);
 
+	ret = dhcp_run(addr, NULL, false);
+	if (ret)
+		return log_msg_ret("dhc", ret);
+
 	log_debug("calling pxe_get()\n");
 	ret = pxe_get(addr, &bootdir, &size, false);
 	log_debug("pxe_get() returned %d\n", ret);