drm/amd/amdgpu: allow use kiq to do hdp flush under sriov

when use cpu to do page table update under sriov runtime, since mmio
access is blocked, kiq has to be used to flush hdp.

change WREG32_NO_KIQ to WREG32 to allow kiq.

Signed-off-by: Victor Zhao <Victor.Zhao@amd.com>
Reviewed-by: Emily Deng <Emily.Deng@amd.com>