Revert "ls1088a: remove dhcp function from u-boot env as boot source"

dhcp boot is a useful feature and works out-of-the-box for ls1088a
platforms. Moreover, no solid reason is given for disabling it.
Revert the patch to re-enable it.

This reverts commit 863e42e8b1f9e97d87919e20e34a7b98089f7522.

Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
Reviewed-by: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>
diff --git a/include/configs/ls1088ardb.h b/include/configs/ls1088ardb.h
index f52ea4d..6387b19 100644
--- a/include/configs/ls1088ardb.h
+++ b/include/configs/ls1088ardb.h
@@ -577,7 +577,8 @@
 
 #define BOOT_TARGET_DEVICES(func) \
 	func(MMC, mmc, 0) \
-	func(SCSI, scsi, 0)
+	func(SCSI, scsi, 0) \
+	func(DHCP, dhcp, na)
 #include <config_distro_bootcmd.h>
 #endif