drm/i915: Disable unused-but-set compiler warning

drm/i915: Disable unused-but-set compiler warning

The unused-but-set warning enabled by W=1 catches out a lot of the
atomic helper iterator macros and drown us in their noise (or trip over
Werror and die). Path of least resistance is to ignore the warning.

Signed-off-by: Chris Wilson <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Cc: Maarten Lankhorst <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
Reviewed-by: Joonas Lahtinen <[email protected]>
Reviewed-by: Maarten Lankhorst <[email protected]>