drm/i915: Copy default modparams to mock i915_device

Since we use the module parameters stored inside the drm_i915_device
itself, we need to ensure the mock i915_device also sets up the right
defaults.

Fixes: 8a25c4be ("drm/i915/params: switch to device specific parameters")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200728150600.4509-1-chris@chris-wilson.co.uk


Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>