drm/i915: Mark pin flags as u64

Since the flags are being used to operate on a u64 variable, they too
need to be marked as such so that the inverses are full width (and not
zero extended on 32b kernels and bdw+).

Reported-by: Sergii Romantsov <sergii.romantsov@globallogic.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@vger.kernel.org
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181102161232.17742-2-chris@chris-wilson.co.uk