Fix 'no return value' in other route(..);

The alternative route(..) was declared as unsigned short but was not
return anything.

control_sgtl5000.h

@@ -58,7 +58,7 @@ public:
 	//bool inputMic(void) { return write(0x002A, 0x0172) && write(0x0024, ana_ctrl & ~(1<<2)); }
 
 	unsigned short route(uint8_t i2s_out, uint8_t dac, uint8_t dap, uint8_t dap_mix);
-	unsigned short route(uint8_t i2s_out, uint8_t dac, uint8_t dap) { route(i2s_out,dac,dap,0); }
+	unsigned short route(uint8_t i2s_out, uint8_t dac, uint8_t dap) { return route(i2s_out,dac,dap,0); }
 	bool volume(float left, float right);
 	unsigned short micGain(unsigned int n) { return modify(0x002A, n&3, 3); }
 	unsigned short lo_lvl(uint8_t n);