drm/amd/pm: remove unneeded variable

fix the following coccicheck warning:

drivers/gpu/drm/amd/pm/swsmu/smu11/navi10_ppt.c:1657:14-18: Unneeded variable: "size".
Signed-off-by: Mingtong Bao <baomingtong001@208suo.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/pm/swsmu/smu11/navi10_ppt.c

@@ -1654,7 +1654,7 @@ static int navi10_force_clk_levels(struct smu_context *smu,
 				   enum smu_clk_type clk_type, uint32_t mask)
 {
 
-	int ret = 0, size = 0;
+	int ret = 0;
 	uint32_t soft_min_level = 0, soft_max_level = 0, min_freq = 0, max_freq = 0;
 
 	soft_min_level = mask ? (ffs(mask) - 1) : 0;
@@ -1675,15 +1675,15 @@ static int navi10_force_clk_levels(struct smu_context *smu,
 
 		ret = smu_v11_0_get_dpm_freq_by_index(smu, clk_type, soft_min_level, &min_freq);
 		if (ret)
-			return size;
+			return 0;
 
 		ret = smu_v11_0_get_dpm_freq_by_index(smu, clk_type, soft_max_level, &max_freq);
 		if (ret)
-			return size;
+			return 0;
 
 		ret = smu_v11_0_set_soft_freq_limited_range(smu, clk_type, min_freq, max_freq);
 		if (ret)
-			return size;
+			return 0;
 		break;
 	case SMU_DCEFCLK:
 		dev_info(smu->adev->dev,"Setting DCEFCLK min/max dpm level is not supported!\n");
@@ -1693,7 +1693,7 @@ static int navi10_force_clk_levels(struct smu_context *smu,
 		break;
 	}
 
-	return size;
+	return 0;
 }
 
 static int navi10_populate_umd_state_clk(struct smu_context *smu)