drm/amdgpu: Extend KIQ reg polling wait for VF

Runtime KIQ interface to read/write registers in VF may take longer
than expected for BM environment. Extend the timeout.

Signed-off-by: Victor Skvortsov <victor.skvortsov@amd.com>
Reviewed-by: Zhigang Luo <zhigang.luo@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>