rename bscconfig.h to config.h, cleanup

Get rid of the legacy name bscconfig.h from osmo-nitb times.

Remove the #include from some of the files that aren't actually using it.

Instead of '#include "../../config.h"', use plain '#include "config.h"'
because we're anyway passing $top_srcdir as -I during compilation.

Change-Id: Id4f683be1f36f0630c83da54e02868aae847aeec
diff --git a/src/libmsc/msc_net_init.c b/src/libmsc/msc_net_init.c
index 51e8595..637ee74 100644
--- a/src/libmsc/msc_net_init.c
+++ b/src/libmsc/msc_net_init.c
@@ -21,7 +21,7 @@
  *
  */
 
-#include "bscconfig.h"
+#include "config.h"
 
 #include <osmocom/core/tdef.h>