drm/amd/pm: drop unnecessary feature->mutex lock protections(V2)

As these operations are performed in hardware setup and there
is actually no race conditions during this period considering:
1. the hardware setup is serial and cannot be in parallel
2. all other operations can be performed only after hardware
   setup complete.

V2: rich the commit log description
Signed-off-by: Evan Quan <evan.quan@amd.com>
Acked-by: Nirmoy Das <nirmoy.das@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/pm/swsmu/amdgpu_smu.c

@@ -361,20 +361,16 @@ static int smu_get_driver_allowed_feature_mask(struct smu_context *smu)
 	int ret = 0;
 	uint32_t allowed_feature_mask[SMU_FEATURE_MAX/32];
 
-	mutex_lock(&feature->mutex);
 	bitmap_zero(feature->allowed, SMU_FEATURE_MAX);
-	mutex_unlock(&feature->mutex);
 
 	ret = smu_get_allowed_feature_mask(smu, allowed_feature_mask,
 					     SMU_FEATURE_MAX/32);
 	if (ret)
 		return ret;
 
-	mutex_lock(&feature->mutex);
 	bitmap_or(feature->allowed, feature->allowed,
 		      (unsigned long *)allowed_feature_mask,
 		      feature->feature_num);
-	mutex_unlock(&feature->mutex);
 
 	return ret;
 }

drivers/gpu/drm/amd/pm/swsmu/smu11/smu_v11_0.c

@@ -721,7 +721,6 @@ int smu_v11_0_set_allowed_mask(struct smu_context *smu)
 	int ret = 0;
 	uint32_t feature_mask[2];
 
-	mutex_lock(&feature->mutex);
 	if (bitmap_empty(feature->allowed, SMU_FEATURE_MAX) || feature->feature_num < 64)
 		goto failed;
 
@@ -738,7 +737,6 @@ int smu_v11_0_set_allowed_mask(struct smu_context *smu)
 		goto failed;
 
 failed:
-	mutex_unlock(&feature->mutex);
 	return ret;
 }