drm/i915/perf: Initialise the dynamic sysfs attr

Use sysfs_attr_init() to dynamically initialise the
oa_config->sysfs_metric_id.attr as it has the important side-effect of
setting the lockdep key.

[    4.971513] [drm] Initialized i915 1.6.0 20170731 for 0000:00:02.0 on minor 0
[    4.973489] BUG: key ffff88026f6e7bb0 not in .data!
[    4.973506] DEBUG_LOCKS_WARN_ON(1)
[    4.973518] ------------[ cut here ]------------
[    4.973547] WARNING: CPU: 1 PID: 258 at kernel/locking/lockdep.c:3156 lockdep_init_map+0x1b2/0x1c0
[    4.973567] Modules linked in: i915(+) x86_pkg_temp_thermal intel_powerclamp coretemp crct10dif_pclmul crc32_pclmul ghash_clmulni_intel snd_hda_intel snd_hda_codec snd_hwdep snd_hda_core snd_pcm r8169 mei_me mii mei lpc_ich prime_numbers i2c_hid pinctrl_broxton pinctrl_intel
[    4.973645] CPU: 1 PID: 258 Comm: systemd-udevd Not tainted 4.13.0-rc3-CI-CI_DRM_2915+ #1
[    4.973664] Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./J4205-ITX, BIOS P1.10 09/29/2016
[    4.973686] task: ffff8802704c2740 task.stack: ffffc90000224000
[    4.973700] RIP: 0010:lockdep_init_map+0x1b2/0x1c0
[    4.973712] RSP: 0018:ffffc90000227a10 EFLAGS: 00010282
[    4.973726] RAX: 0000000000000016 RBX: ffff880262aac010 RCX: 0000000000000000
[    4.973741] RDX: 0000000080000001 RSI: 0000000000000001 RDI: ffffffff810ed1ab
[    4.973757] RBP: ffffc90000227a30 R08: 0000000000000001 R09: 0000000000000000
[    4.973774] R10: 0000000000000000 R11: 0000000000000000 R12: ffff88026f6e7bb0
[    4.973789] R13: 0000000000000000 R14: ffff88026f6e7b98 R15: ffffffff81a24da0
[    4.973805] FS:  00007f588d7f58c0(0000) GS:ffff88027fc80000(0000) knlGS:0000000000000000
[    4.973823] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    4.973837] CR2: 00000082482e32a0 CR3: 0000000270531000 CR4: 00000000003406e0
[    4.973852] Call Trace:
[    4.973864]  __kernfs_create_file+0x71/0xe0
[    4.973876]  sysfs_add_file_mode_ns+0x85/0x1a0
[    4.973890]  internal_create_group+0xe5/0x2b0
[    4.973903]  sysfs_create_group+0xe/0x10
[    4.973985]  i915_perf_register+0xd9/0x220 [i915]
[    4.974044]  i915_driver_load+0xa72/0x16b0 [i915]
[    4.974124]  i915_pci_probe+0x32/0x90 [i915]

Annoyingly detected by CI, but not reported due to it occurring during boot
and disabling lockdep for later runs.

Fixes: f89823c21224 ("drm/i915/perf: Implement I915_PERF_ADD/REMOVE_CONFIG interface")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Andrzej Datczuk <andrzej.datczuk@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170803223700.10329-1-chris@chris-wilson.co.uk
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>

drivers/gpu/drm/i915/i915_perf.c

@@ -3117,6 +3117,7 @@ static ssize_t show_dynamic_id(struct device *dev,
 static int create_dynamic_oa_sysfs_entry(struct drm_i915_private *dev_priv,
 					 struct i915_oa_config *oa_config)
 {
+	sysfs_attr_init(&oa_config->sysfs_metric_id.attr);
 	oa_config->sysfs_metric_id.attr.name = "id";
 	oa_config->sysfs_metric_id.attr.mode = S_IRUGO;
 	oa_config->sysfs_metric_id.show = show_dynamic_id;