drm/i915: remove redundant variable hw_check

hw_check is being assigned and updated but is no longer being read,
hence it is redundant and can be removed.

Detected by clang scan-build:
"warning: Value stored to 'hw_check' during its initialization
is never read"

Fixes: f6d1973d ("drm/i915: Move modeset state verifier calls")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20170914162154.11304-1-colin.king@canonical.com