drm/msm/mdp5: Fix global state lock backoff

We need to grab the lock after the early return for !hwpipe case.
Otherwise, we could have hit contention yet still returned 0.

Fixes an issue that the new CONFIG_DRM_DEBUG_MODESET_LOCK stuff flagged
in CI:

   WARNING: CPU: 0 PID: 282 at drivers/gpu/drm/drm_modeset_lock.c:296 drm_modeset_lock+0xf8/0x154
   Modules linked in:
   CPU: 0 PID: 282 Comm: kms_cursor_lega Tainted: G        W         5.19.0-rc2-15930-g875cc8bc536a #1
   Hardware name: Qualcomm Technologies, Inc. DB820c (DT)
   pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
   pc : drm_modeset_lock+0xf8/0x154
   lr : drm_atomic_get_private_obj_state+0x84/0x170
   sp : ffff80000cfab6a0
   x29: ffff80000cfab6a0 x28: 0000000000000000 x27: ffff000083bc4d00
   x26: 0000000000000038 x25: 0000000000000000 x24: ffff80000957ca58
   x23: 0000000000000000 x22: ffff000081ace080 x21: 0000000000000001
   x20: ffff000081acec18 x19: ffff80000cfabb80 x18: 0000000000000038
   x17: 0000000000000000 x16: 0000000000000000 x15: fffffffffffea0d0
   x14: 0000000000000000 x13: 284e4f5f4e524157 x12: 5f534b434f4c5f47
   x11: ffff80000a386aa8 x10: 0000000000000029 x9 : ffff80000cfab610
   x8 : 0000000000000029 x7 : 0000000000000014 x6 : 0000000000000000
   x5 : 0000000000000001 x4 : ffff8000081ad904 x3 : 0000000000000029
   x2 : ffff0000801db4c0 x1 : ffff80000cfabb80 x0 : ffff000081aceb58
   Call trace:
    drm_modeset_lock+0xf8/0x154
    drm_atomic_get_private_obj_state+0x84/0x170
    mdp5_get_global_state+0x54/0x6c
    mdp5_pipe_release+0x2c/0xd4
    mdp5_plane_atomic_check+0x2ec/0x414
    drm_atomic_helper_check_planes+0xd8/0x210
    drm_atomic_helper_check+0x54/0xb0
    ...
   ---[ end trace 0000000000000000 ]---
   drm_modeset_lock attempting to lock a contended lock without backoff:
      drm_modeset_lock+0x148/0x154
      mdp5_get_global_state+0x30/0x6c
      mdp5_pipe_release+0x2c/0xd4
      mdp5_plane_atomic_check+0x290/0x414
      drm_atomic_helper_check_planes+0xd8/0x210
      drm_atomic_helper_check+0x54/0xb0
      drm_atomic_check_only+0x4b0/0x8f4
      drm_atomic_commit+0x68/0xe0

Fixes: d59be579 ("drm/msm/mdp5: Return error code in mdp5_pipe_release when deadlock is detected")
Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/492701/
Link: https://lore.kernel.org/r/20220707162040.1594855-1-robdclark@gmail.com

drivers/gpu/drm/msm/disp/mdp5/mdp5_pipe.c

@@ -123,12 +123,13 @@ int mdp5_pipe_release(struct drm_atomic_state *s, struct mdp5_hw_pipe *hwpipe)
 {
 	struct msm_drm_private *priv = s->dev->dev_private;
 	struct mdp5_kms *mdp5_kms = to_mdp5_kms(to_mdp_kms(priv->kms));
-	struct mdp5_global_state *state = mdp5_get_global_state(s);
+	struct mdp5_global_state *state;
 	struct mdp5_hw_pipe_state *new_state;
 
 	if (!hwpipe)
 		return 0;
 
+	state = mdp5_get_global_state(s);
 	if (IS_ERR(state))
 		return PTR_ERR(state);