drm/msm: cleanup: drm_modeset_lock_all_ctx() --> DRM_MODESET_LOCK_ALL_BEGIN()

As requested in Documentation/gpu/todo.rst, replace the boilerplate code
surrounding drm_modeset_lock_all_ctx() with DRM_MODESET_LOCK_ALL_BEGIN()
and DRM_MODESET_LOCK_ALL_END()
Signed-off-by: Fernando Ramos <greenfoo@u92.eu>
Reviewed-by: Sean Paul <sean@poorly.run>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210924064324.229457-4-greenfoo@u92.eu

drivers/gpu/drm/msm/disp/msm_disp_snapshot_util.c

@@ -5,6 +5,8 @@
 
 #define pr_fmt(fmt)	"[drm:%s:%d] " fmt, __func__, __LINE__
 
+#include <drm/drm_drv.h>
+
 #include "msm_disp_snapshot.h"
 
 static void msm_disp_state_dump_regs(u32 **reg, u32 aligned_len, void __iomem *base_addr)
@@ -99,20 +101,18 @@ static void msm_disp_capture_atomic_state(struct msm_disp_state *disp_state)
 {
 	struct drm_device *ddev;
 	struct drm_modeset_acquire_ctx ctx;
+	int ret;
 
 	disp_state->timestamp = ktime_get();
 
 	ddev = disp_state->drm_dev;
 
-	drm_modeset_acquire_init(&ctx, 0);
-
-	while (drm_modeset_lock_all_ctx(ddev, &ctx) != 0)
-		drm_modeset_backoff(&ctx);
+	DRM_MODESET_LOCK_ALL_BEGIN(ddev, ctx, 0, ret);
 
 	disp_state->atomic_state = drm_atomic_helper_duplicate_state(ddev,
 			&ctx);
-	drm_modeset_drop_locks(&ctx);
-	drm_modeset_acquire_fini(&ctx);
+
+	DRM_MODESET_LOCK_ALL_END(ddev, ctx, ret);
 }
 
 void msm_disp_snapshot_capture_state(struct msm_disp_state *disp_state)