drm/msm/dpu: Fix smatch warnings about variable dereferenced before check

Fix below smatch warnings:
drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp_v13.c:161 dpu_hw_sspp_setup_pe_config_v13()
warn: variable dereferenced before check 'ctx' (see line 159)

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Closes: https://lore.kernel.org/r/202601252214.oEaY3UZM-lkp@intel.com/
Signed-off-by: sunliming <sunliming@kylinos.cn>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/701853/
Link: https://lore.kernel.org/r/20260130053615.24886-1-sunliming@linux.dev
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>

Author: sunliming

drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp_v13.c

@@ -156,11 +156,13 @@ static void dpu_hw_sspp_setup_pe_config_v13(struct dpu_hw_sspp *ctx,
 	u8 color;
 	u32 lr_pe[4], tb_pe[4];
 	const u32 bytemask = 0xff;
-	u32 offset = ctx->cap->sblk->sspp_rec0_blk.base;
+	u32 offset;
 
 	if (!ctx || !pe_ext)
 		return;
 
+	offset = ctx->cap->sblk->sspp_rec0_blk.base;
+
 	c = &ctx->hw;
 	/* program SW pixel extension override for all pipes*/
 	for (color = 0; color < DPU_MAX_PLANES; color++) {