drm/msm/disp/dpu1/dpu_hw_lm: Fix misnaming of parameter 'ctx'

Fixes the following W=1 kernel build warning(s):

 drivers/gpu/drm/msm/disp/dpu1/dpu_hw_lm.c:55: warning: Function parameter or member 'ctx' not described in '_stage_offset'
 drivers/gpu/drm/msm/disp/dpu1/dpu_hw_lm.c:55: warning: Excess function parameter 'c' description in '_stage_offset'

Cc: Rob Clark <robdclark@gmail.com>
Cc: Sean Paul <sean@poorly.run>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: linux-arm-msm@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: freedreno@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Abhinav Kumar <abhinavk@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>