drm/msm/dsi: initialize postdiv_lock before use for 10nm pll

postdiv_lock spinlock was used before initialization
for 10nm pll. It causes following spin_bug:
	"BUG: spinlock bad magic on CPU#0".
Initialize spinlock before its usage.

Changes in v3:
- Added Archit's R-b
Reviewed-by: NArchit Taneja <architt@codeaurora.org>
Signed-off-by: NRajesh Yadav <ryadav@codeaurora.org>
Signed-off-by: NSean Paul <seanpaul@chromium.org>
Signed-off-by: NRob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/dsi/pll/dsi_pll_10nm.c

@@ -798,6 +798,8 @@ struct msm_dsi_pll *msm_dsi_pll_10nm_init(struct platform_device *pdev, int id)
 		return ERR_PTR(-ENOMEM);
 	}
 
+	spin_lock_init(&pll_10nm->postdiv_lock);
+
 	pll = &pll_10nm->base;
 	pll->min_rate = 1000000000UL;
 	pll->max_rate = 3500000000UL;