drm/amdgpu: add pcie cap module parameters (v2)

Allows the user to force the supported pcie gen and lane
config on both the asic and the chipset.
Useful for debugging pcie problems and for virtualization
where we may not be able to query the pcie bridge caps.

Default to:
gen: chipset 1/2, asic 1/2/3
lanes: 1/2/4/8/16

v2: fix bare metal case

Reviewed-by: monk liu <monk.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index 82edf95..4021c8a 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -87,6 +87,8 @@
 extern int amdgpu_sched_hw_submission;
 extern int amdgpu_enable_semaphores;
 extern int amdgpu_powerplay;
+extern unsigned amdgpu_pcie_gen_cap;
+extern unsigned amdgpu_pcie_lane_cap;
 
 #define AMDGPU_WAIT_IDLE_TIMEOUT_IN_MS	        3000
 #define AMDGPU_MAX_USEC_TIMEOUT			100000	/* 100 ms */