Change configure define USRP1 to DEVICE_USRP1

Similar as we do for ARCH_*, it's easier to find those are related to
device support features.

Change-Id: Iba238bff689b8f944af76120402c0fa2e29a70de
diff --git a/Transceiver52M/device/Makefile.am b/Transceiver52M/device/Makefile.am
index 8575328..f0675b0 100644
--- a/Transceiver52M/device/Makefile.am
+++ b/Transceiver52M/device/Makefile.am
@@ -4,7 +4,7 @@
 
 SUBDIRS =
 
-if USRP1
+if DEVICE_USRP1
 SUBDIRS += usrp1
 else
 SUBDIRS += uhd