drm/i915/gvt: Give new born vGPU higher scheduling chance

drm/i915/gvt: Give new born vGPU higher scheduling chance

This trys to give new born vGPU with higher scheduling chance
not only with adding to sched list head and also have higher
priority for workload sched for 2 seconds after starting to
schedule it. In order for fast GPU execution during VM boot,
and ensure guest driver setup with required state given in time.

This fixes recent failure seen on one VM with multiple linux VMs
running on kernel with commit 894a686213785("drm/i915: Provide a timeout to i915_gem_wait_for_idle() on setup"),
which had shorter setup timeout that caused context state init failed.

v2: change to 2s for higher scheduling period

Cc: Yuan Hang <hang.yuan@intel.com>
Reviewed-by: Hang Yuan <hang.yuan@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>