devfreq_cooling: no need to check state with negative number

We could see that state is defined as unsigned type, so it
should never be less than zero. Let' remove this check.
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>

drivers/thermal/devfreq_cooling.c

@@ -312,7 +312,7 @@ static int devfreq_cooling_state2power(struct thermal_cooling_device *cdev,
 	unsigned long freq;
 	u32 static_power;
 
-	if (state < 0 || state >= dfc->freq_table_size)
+	if (state >= dfc->freq_table_size)
 		return -EINVAL;
 
 	freq = dfc->freq_table[state];