subdev/clk: fix repeated words in comments

 Delete the redundant word 'at'.
Signed-off-by: wangjianli <wangjianli@cdjrlc.com>
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220821143038.46589-1-wangjianli@cdjrlc.com

drivers/gpu/drm/nouveau/nvkm/subdev/clk/gm20b.c

@@ -581,7 +581,7 @@ gm20b_clk_prog(struct nvkm_clk *base)
 
 	/*
 	 * Interim step for changing DVFS detection settings: low enough
-	 * frequency to be safe at at DVFS coeff = 0.
+	 * frequency to be safe at DVFS coeff = 0.
 	 *
 	 * 1. If voltage is increasing:
 	 * - safe frequency target matches the lowest - old - frequency