drm/amdgpu: drop ih reroute function from psp v11

For all the ASICs that integrate psp v11, vega20
doesn't support ih reroute. arcturus and later will
allow kernel driver to program ih_cfg_index/data
through mmio directly. navi1x and onwards will only
support grb_ih_set command in sriov configuration.

psp_v11_0_reroute_ih is not needed any more.

Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>