drm/i915/gt: Pull intel_gt_init_hw() into intel_gt_resume()

Since intel_gt_resume() is always immediately proceeded by init_hw, pull
the call into intel_gt_resume, where we have the rpm and fw already
held.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Andi Shyti <andi.shyti@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191222144046.1674865-1-chris@chris-wilson.co.uk