drm/amdgpu: Fix stub function name

This function was renamed in a previous commit. Update the stub
function name for builds with CONFIG_HSA_AMD disabled.

Fixes: 611736d8

 ("drm/amdgpu: Add KFD VRAM limit checking")
Acked-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>