drm/amdgpu/gfx: fix off by one in rb rework (v2)

When I reworked this code, I messed up num rb count.

v2: use hweight32
Reviewed-by: Ken Wang <Qingquing.Wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/gfx_v7_0.c

@@ -1635,7 +1635,7 @@ static u32 gfx_v7_0_get_rb_active_bitmap(struct amdgpu_device *adev)
 static void gfx_v7_0_setup_rb(struct amdgpu_device *adev)
 {
 	int i, j;
-	u32 data, tmp, num_rbs = 0;
+	u32 data;
 	u32 active_rbs = 0;
 
 	mutex_lock(&adev->grbm_idx_mutex);
@@ -1655,10 +1655,7 @@ static void gfx_v7_0_setup_rb(struct amdgpu_device *adev)
 	mutex_unlock(&adev->grbm_idx_mutex);
 
 	adev->gfx.config.backend_enable_mask = active_rbs;
-	tmp = active_rbs;
-	while (tmp >>= 1)
-		num_rbs++;
-	adev->gfx.config.num_rbs = num_rbs;
+	adev->gfx.config.num_rbs = hweight32(active_rbs);
 }
 
 /**

drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c

@@ -2613,7 +2613,7 @@ static u32 gfx_v8_0_get_rb_active_bitmap(struct amdgpu_device *adev)
 static void gfx_v8_0_setup_rb(struct amdgpu_device *adev)
 {
 	int i, j;
-	u32 data, tmp, num_rbs = 0;
+	u32 data;
 	u32 active_rbs = 0;
 
 	mutex_lock(&adev->grbm_idx_mutex);
@@ -2629,10 +2629,7 @@ static void gfx_v8_0_setup_rb(struct amdgpu_device *adev)
 	mutex_unlock(&adev->grbm_idx_mutex);
 
 	adev->gfx.config.backend_enable_mask = active_rbs;
-	tmp = active_rbs;
-	while (tmp >>= 1)
-		num_rbs++;
-	adev->gfx.config.num_rbs = num_rbs;
+	adev->gfx.config.num_rbs = hweight32(active_rbs);
 }
 
 /**