drm/amdgpu: use multipipe compute policy on non PL11 asics

A performance regression for OpenCL tests on Polaris11 had this feature
disabled for all asics.

Instead, disable it selectively on the affected asics.

Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Andres Rodriguez <andresx7@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>