drm/amdkfd: drop struct kfd_cu_info

I think this was an abstraction back from when
kfd supported both radeon and amdgpu.  Since we just
support amdgpu now, there is no more need for this and
we can use the amdgpu structures directly.

This also avoids having the kfd_cu_info structures on
the stack when inlining which can blow up the stack.

Cc: Arnd Bergmann <arnd@kernel.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>