drm/i915: Fix uninitialized mask in intel_device_info_subplatform_init

drm/i915: Fix uninitialized mask in intel_device_info_subplatform_init

Mask need to be initialized to zero since device id checks may not match.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 805446c8347c ("drm/i915: Introduce concept of a sub-platform")
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Jose Souza <jose.souza@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190403064407.25646-1-tvrtko.ursulin@linux.intel.com