drm/amdgpu/soc15: Fix static checker warnings

vega10 is the only soc15 asic at the moment so these
warnings are invalid, but add a default case to silence
the warnings.

Fixes: 220ab9bd1ccf: "drm/amdgpu: soc15 enable (v3)"
Reviewed-by: Junwei Zhang <Jerry.Zhang@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/soc15.c

@@ -106,6 +106,8 @@ static u32 soc15_pcie_rreg(struct amdgpu_device *adev, u32 reg)
 
 	if (adev->asic_type == CHIP_VEGA10)
 		nbio_pcie_id = &nbio_v6_1_pcie_index_data;
+	else
+		BUG();
 
 	address = nbio_pcie_id->index_offset;
 	data = nbio_pcie_id->data_offset;
@@ -125,6 +127,8 @@ static void soc15_pcie_wreg(struct amdgpu_device *adev, u32 reg, u32 v)
 
 	if (adev->asic_type == CHIP_VEGA10)
 		nbio_pcie_id = &nbio_v6_1_pcie_index_data;
+	else
+		BUG();
 
 	address = nbio_pcie_id->index_offset;
 	data = nbio_pcie_id->data_offset;