drm/i915/gvt: Remove bogus retry around i915_wait_request

drm/i915/gvt: Remove bogus retry around i915_wait_request

commit 8f1117abb408 ("drm/i915/gvt: handle workload lifecycle properly")
includes some nonsense to retry a indefinite wait - i915_wait_request()
does not return until the request is completed when used from an
uninterruptible context.

Fixes: 8f1117abb408 ("drm/i915/gvt: handle workload lifecycle properly"
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Chuanxiao Dong <chuanxiao.dong@intel.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Cc: Zhi Wang <zhi.a.wang@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>