[devel] Fix DIAG_MODE definition. Fixes: JB#32805

With the new libusbmoded-qt it pulls the definitions from the usb-moded
headers, which apparently are faulty.

Related:
https://github.com/nemomobile/libusb-moded-qt/blob/master/src/qusbmode.cpp

Signed-off-by: Philippe De Swert <philippe.deswert@jollamobile.com>

src/usb_moded-modes.h

@@ -29,7 +29,7 @@
 #define MODE_MTP		"mtp_mode"
 #define MODE_HOST		"host_mode"
 #define MODE_CONNECTION_SHARING "connection_sharing"
-#define MODE_DIAG		"qa_diag_mode"
+#define MODE_DIAG		"diag_mode"
 #define MODE_ADB		"adb_mode"
 #define MODE_PC_SUITE		"pc_suite"
 #define MODE_CHARGING           "charging_only"