core: new '--test-multiplex-requested' option

The new option will change the default setting in MBIM and QMI bearers
to "request" when no explicit "multiplex" configuration is given by
the user.

This option will help test the multiplexing support in the modems
before it's made a default in a future release.

src/mm-context.h

@@ -54,7 +54,8 @@ gboolean     mm_context_get_test_no_suspend_resume (void);
 gboolean     mm_context_get_test_quick_suspend_resume (void);
 #endif
 #if defined WITH_QRTR
-gboolean     mm_context_get_test_no_qrtr    (void);
+gboolean     mm_context_get_test_no_qrtr (void);
 #endif
+gboolean     mm_context_get_test_multiplex_requested (void);
 
 #endif /* MM_CONTEXT_H */