Revert "drm/i915: use localized __diag_ignore_all() instead of per file"

Revert "drm/i915: use localized __diag_ignore_all() instead of per file"

This reverts commit 88e9664434c994e97a9f6f8cdd1535495c660cea.

__diag_ignore_all() only works for GCC 8 or later.

-Woverride-init (from -Wextra, enabled in i915 Makefile) combined with
CONFIG_WERROR=y or W=e breaks the build for older GCC.

With i386_defconfig and x86_64_defconfig enabling CONFIG_WERROR=y by
default, we really need to roll back the change.

An alternative would be to disable -Woverride-init in the Makefile for
GCC <8, but the revert seems like the safest bet now.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/8768
Reported-by: John Garry <john.g.garry@oracle.com>
References: https://lore.kernel.org/r/ad2601c0-84bb-c574-3702-a83ff8faf98c@oracle.com
References: https://lore.kernel.org/r/87wmzezns4.fsf@intel.com
Fixes: 88e9664434c9 ("drm/i915: use localized __diag_ignore_all() instead of per file")
Cc: Gustavo Sousa <gustavo.sousa@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Tested-by: John Garry <john.g.garry@oracle.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230711110214.25093-1-jani.nikula@intel.com