drm/i915: remove i915_drm_client::id

i915_drm_client::id is not used since commit e894b724c316 (drm/i915:
Use the fdinfo helper). Drop it.

Found by https://github.com/jirislaby/clang-struct.

Signed-off-by: Jiri Slaby (SUSE) <[e-mail]>
Cc: Jani Nikula <[e-mail]>
Cc: Joonas Lahtinen <[e-mail]>
Cc: Rodrigo Vivi <[e-mail]>
Cc: Tvrtko Ursulin <[e-mail]>
Cc: [e-mail]
Acked-by: Jani Nikula <[e-mail]>
Signed-off-by: Rodrigo Vivi <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/i915/i915_drm_client.h

···
 struct i915_drm_client {
 	struct kref kref;
 
-	unsigned int id;
-
 	spinlock_t ctx_lock; /* For add/remove from ctx_list. */
 	struct list_head ctx_list; /* List of contexts belonging to client. */