drm/omapdrm: cleanup: drm_modeset_lock_all() --> DRM_MODESET_LOCK_ALL_BEGIN()

As requested in Documentation/gpu/todo.rst, replace driver calls to
drm_modeset_lock_all() 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>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210924064324.229457-10-greenfoo@u92.eu

drivers/gpu/drm/omapdrm/omap_fb.c

@@ -9,6 +9,7 @@
 #include <drm/drm_modeset_helper.h>
 #include <drm/drm_fourcc.h>
 #include <drm/drm_gem_framebuffer_helper.h>
+#include <drm/drm_drv.h>
 
 #include "omap_dmm_tiler.h"
 #include "omap_drv.h"
@@ -62,15 +63,17 @@ static int omap_framebuffer_dirty(struct drm_framebuffer *fb,
 				  unsigned num_clips)
 {
 	struct drm_crtc *crtc;
+	struct drm_modeset_acquire_ctx ctx;
+	int ret;
 
-	drm_modeset_lock_all(fb->dev);
+	DRM_MODESET_LOCK_ALL_BEGIN(fb->dev, ctx, 0, ret);
 
 	drm_for_each_crtc(crtc, fb->dev)
 		omap_crtc_flush(crtc);
 
-	drm_modeset_unlock_all(fb->dev);
+	DRM_MODESET_LOCK_ALL_END(fb->dev, ctx, ret);
 
-	return 0;
+	return ret;
 }
 
 static const struct drm_framebuffer_funcs omap_framebuffer_funcs = {