hwmon: (sis5595) drop unused DIV_TO_REG function

'DIV_TO_REG' function is not used:

  sis5595.c:159:18: error: unused function 'DIV_TO_REG' [-Werror,-Wunused-function]
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20240225202841.60740-1-krzysztof.kozlowski@linaro.orgSigned-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/sis5595.c

@@ -153,13 +153,9 @@ static inline s8 TEMP_TO_REG(long val)
 }
 
 /*
- * FAN DIV: 1, 2, 4, or 8 (defaults to 2)
- * REG: 0, 1, 2, or 3 (respectively) (defaults to 1)
+ * FAN DIV: 1, 2, 4, or 8
+ * REG: 0, 1, 2, or 3 (respectively)
  */
-static inline u8 DIV_TO_REG(int val)
-{
-	return val == 8 ? 3 : val == 4 ? 2 : val == 1 ? 0 : 1;
-}
 #define DIV_FROM_REG(val) (1 << (val))
 
 /*