drm/i915: Extend I915_PARAMS_FOR_EACH with default member value

By combining default value into helper macro we can initialize
modparams struct in the same automatic way as it was declared.
This will initialize members in the same order as declared
and additionally will disallow declaring new member without
proper default value for it.

v2: make MEMBER macro more robust (Joonas)

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170925105008.46060-2-michal.wajdeczko@intel.com