drm/amd/pm: correct string parsing for extra separator characters case

Supplement of previous fix.
Signed-off-by: Evan Quan <evan.quan@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -1870,6 +1870,8 @@ static ssize_t amdgpu_set_pp_power_profile_mode(struct device *dev,
 		memcpy(buf_cpy, buf, count-i);
 		tmp_str = buf_cpy;
 		while ((sub_str = strsep(&tmp_str, delimiter)) != NULL) {
+			if (strlen(sub_str) == 0)
+				continue;
 			ret = kstrtol(sub_str, 0, &parameter[parameter_size]);
 			if (ret)
 				return -EINVAL;