amdgpu/soc15: make the pcie index/data registers constant.

These don't seem to change at runtime, and the initialisers
are constant data. This could be improved by not selecting
the apu/non-apu path on each pcie read/write access.

Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/amd/amdgpu/soc15.c b/drivers/gpu/drm/amd/amdgpu/soc15.c
index 245a18a..dd5cbf3 100644
--- a/drivers/gpu/drm/amd/amdgpu/soc15.c
+++ b/drivers/gpu/drm/amd/amdgpu/soc15.c
@@ -101,7 +101,7 @@ static u32 soc15_pcie_rreg(struct amdgpu_device *adev, u32 reg)
 {
 	unsigned long flags, address, data;
 	u32 r;
-	struct nbio_pcie_index_data *nbio_pcie_id;
+	const struct nbio_pcie_index_data *nbio_pcie_id;
 
 	if (adev->flags & AMD_IS_APU)
 		nbio_pcie_id = &nbio_v7_0_pcie_index_data;
@@ -122,7 +122,7 @@ static u32 soc15_pcie_rreg(struct amdgpu_device *adev, u32 reg)
 static void soc15_pcie_wreg(struct amdgpu_device *adev, u32 reg, u32 v)
 {
 	unsigned long flags, address, data;
-	struct nbio_pcie_index_data *nbio_pcie_id;
+	const struct nbio_pcie_index_data *nbio_pcie_id;
 
 	if (adev->flags & AMD_IS_APU)
 		nbio_pcie_id = &nbio_v7_0_pcie_index_data;