fixup! Refactor: Add defs_bpm.h

src/engine/controls/bpm/defs_bpm.h

@@ -1,8 +1,12 @@
 #pragma once
 
 namespace mixxx {
-// Nominal value range supported by the "bpm" control
-// (although out-of-bounds values are supported)
+// Nominal value range supported by the 'bpm' CO
+// (although out-of-bounds values are supported).
+//
+// Note that this is different from the BPM value range
+// that is supported by Mixxx internally; for that see
+// mixxx::Bpm::kValueMin and mixxx::Bpm::kValueMax.
 constexpr double kBpmRangeMin = 1.0;
 // TODO(XXX): Change to mixxx::Bpm::kValueMax? This would affect controller mappings!
 constexpr double kBpmRangeMax = 200.0;