configs: ls1088ardb: Add support for usb boot target

LS1088A-RDB has MMC, SCSI, DHCP as boot targets,
but the USB support was missing.
Add support for USB as Boot_targets_devices.
Signed-off-by: NEra Tiwari <era.tiwari@nxp.com>
Signed-off-by: NPramod Kumar <pramod.kumar_1@nxp.com>
[Rebased]
Signed-off-by: NPriyanka Jain <priyanka.jain@nxp.com>

include/configs/ls1088ardb.h

@@ -524,6 +524,7 @@
 
 #define BOOT_TARGET_DEVICES(func) \
 	func(MMC, mmc, 0) \
+	func(USB, usb, 0) \
 	func(SCSI, scsi, 0) \
 	func(DHCP, dhcp, na)
 #include <config_distro_bootcmd.h>