hwmon: (f75375s) Don't crash the kernel unnecessarily

The f75375s driver crashes the kernel if it detects an an internal
implementation error. While the detected conditions suggest that
there is a bug in the code, the condition is not fatal.
Replace BUG() with WARN().

Cc: Riku Voipio <[e-mail]>
Signed-off-by: Guenter Roeck <[e-mail]>

drivers/hwmon/f75375s.c

···
 	case 3: /* Manual, speed mode */
 		return false;
 	default:
-		BUG();
+		WARN(1, "Unexpected pwm_enable value %d\n", pwm_enable);
 		return true;
 	}
 }
···
 	case 4: /* Auto, duty mode */
 		return true;
 	default:
-		BUG();
+		WARN(1, "Unexpected pwm_enable value %d\n", pwm_enable);
 		return false;
 	}
 }