drm/amd/sriov: extend NV_MAILBOX_POLL_MSG_TIMEDOUT

on MI300/MI308 UBB products, when doing mode1 reset, since 1 gpu need to
wait all 8 gpus finish mode1 reset and then do re-init. As observed,
sometimes the gpu which triggered the reset need to wait 15s for all
gpus to finish.

If poll msg timeout, guest driver will send the reset message again, and
may mess up the following reinit sequence on other gpus.

So extend the time to cover the maximum time needed to recover.

Signed-off-by: Victor Zhao <Victor.Zhao@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>