armv8: ls1028a: add dhcp boot target device

Add DHCP boot target device to enable command bootcmd_dhcp.

Signed-off-by: Yuantian Tang <andy.tang@nxp.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>
diff --git a/include/configs/ls1028a_common.h b/include/configs/ls1028a_common.h
index 818bd71..2a38e91 100644
--- a/include/configs/ls1028a_common.h
+++ b/include/configs/ls1028a_common.h
@@ -70,7 +70,8 @@
 #define BOOT_TARGET_DEVICES(func) \
 	func(MMC, mmc, 0) \
 	func(MMC, mmc, 1) \
-	func(USB, usb, 0)
+	func(USB, usb, 0) \
+	func(DHCP, dhcp, na)
 #include <config_distro_bootcmd.h>
 
 /* Initial environment variables */