drm/i915: Make 'i915_gem_check_olr' actually check by request not seqno

Updated the _check_olr() function to actually take a request object and compare
it to the OLR rather than extracting seqnos and comparing those.

Note that there is one use case where the request object being processed is no
longer available at that point in the call stack. Hence a temporary copy of the
original function is still present (but called _check_ols() instead). This will
be removed in a subsequent patch.

Also, downgraded a BUG_ON to a WARN_ON as apparently the former is frowned upon
for shipping code.

For: VIZ-4377
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Reviewed-by: Thomas Daniel <Thomas.Daniel@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>