boards/cc2538dk: use find-tty.sh to locate the board by serial number

boards/cc2538dk/Makefile.include

@@ -2,8 +2,12 @@
 export CPU        = cc2538
 export CPU_MODEL ?= cc2538nf53
 
+# the SmartRF06 Evaluation Board serial numbers all begin with "06EB":
+export PROGRAMMER_SERIAL ?= 06EB
+
 # setup serial terminal
-PORT_LINUX ?= $(firstword $(wildcard /dev/serial/by-id/*XDS100v3*if01* /dev/ttyUSB1))
+# the debug UART is always the second tty with the matching serial number:
+PORT_LINUX ?= $(word 2,$(shell $(RIOTBASE)/dist/tools/usb-serial/find-tty.sh '^$(PROGRAMMER_SERIAL)'))
 PORT_DARWIN ?= $(firstword $(sort $(wildcard /dev/tty.usbserial*)))
 include $(RIOTBOARD)/Makefile.include.serial