Main: add function prototype of float_to_linear16 (impl in 00dc1498)

common/include/float_utils.h

@@ -4,6 +4,7 @@
 #include <stdint.h>
 
 uint16_t float_to_linear(float val);
+uint16_t float_to_linear16(float val);
 float linear_to_float(uint16_t val);
 
 #endif