drm/amdgpu: add an interface to get gfx constants from atombios

Fetch the values from atom rather than hardcoding them in the
driver.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.h
index 9e14420..8c2e696 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.h
@@ -144,6 +144,8 @@
 
 int amdgpu_atombios_get_clock_info(struct amdgpu_device *adev);
 
+int amdgpu_atombios_get_gfx_info(struct amdgpu_device *adev);
+
 bool amdgpu_atombios_get_asic_ss_info(struct amdgpu_device *adev,
 				      struct amdgpu_atom_ss *ss,
 				      int id, u32 clock);