drm/radeon: allow pcie gen2 speed on Cayman

Looks like the same pcie gen2 speed initialization for
Evergreen also works on Cayman and seems to come up fine,
so enable it if the module parameter says so

Signed-off-by: Ilija Hadzic <ihadzic@research.bell-labs.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/radeon/evergreen.c b/drivers/gpu/drm/radeon/evergreen.c
index 1fc8650..5df39bf 100644
--- a/drivers/gpu/drm/radeon/evergreen.c
+++ b/drivers/gpu/drm/radeon/evergreen.c
@@ -39,7 +39,7 @@
 
 static void evergreen_gpu_init(struct radeon_device *rdev);
 void evergreen_fini(struct radeon_device *rdev);
-static void evergreen_pcie_gen2_enable(struct radeon_device *rdev);
+void evergreen_pcie_gen2_enable(struct radeon_device *rdev);
 
 void evergreen_fix_pci_max_read_req_size(struct radeon_device *rdev)
 {
@@ -3317,7 +3317,7 @@
 	rdev->bios = NULL;
 }
 
-static void evergreen_pcie_gen2_enable(struct radeon_device *rdev)
+void evergreen_pcie_gen2_enable(struct radeon_device *rdev)
 {
 	u32 link_width_cntl, speed_cntl;