drm/amd/pm: Fixes incorrect type in 'amdgpu_hwmon_show_power_avg() & _input()'

The val is defined as unsigned int type, if(val<0) is invalid, hence
modified its type to ssize_t

Fixes the below:

drivers/gpu/drm/amd/pm/amdgpu_pm.c:2800:5-8: WARNING: Unsigned expression compared with zero: val < 0
drivers/gpu/drm/amd/pm/amdgpu_pm.c:2813:5-8: WARNING: Unsigned expression compared with zero: val < 0

Cc: Guchun Chen <guchun.chen@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Pan, Xinhui" <Xinhui.Pan@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Asad Kamal <asad.kamal@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/pm/amdgpu_pm.c

@@ -2794,26 +2794,26 @@ static ssize_t amdgpu_hwmon_show_power_avg(struct device *dev,
 					   struct device_attribute *attr,
 					   char *buf)
 {
-	int val;
+	ssize_t val;
 
 	val = amdgpu_hwmon_get_power(dev, AMDGPU_PP_SENSOR_GPU_AVG_POWER);
 	if (val < 0)
 		return val;
 
-	return sysfs_emit(buf, "%u\n", val);
+	return sysfs_emit(buf, "%zd\n", val);
 }
 
 static ssize_t amdgpu_hwmon_show_power_input(struct device *dev,
 					     struct device_attribute *attr,
 					     char *buf)
 {
-	int val;
+	ssize_t val;
 
 	val = amdgpu_hwmon_get_power(dev, AMDGPU_PP_SENSOR_GPU_INPUT_POWER);
 	if (val < 0)
 		return val;
 
-	return sysfs_emit(buf, "%u\n", val);
+	return sysfs_emit(buf, "%zd\n", val);
 }
 
 static ssize_t amdgpu_hwmon_show_power_cap_min(struct device *dev,