i2c: xgene-slimpro: Fix wrong pointer passed to PTR_ERR()

PTR_ERR should access the value just tested by IS_ERR, otherwise
the wrong error code will be returned.

Fixes: 7b6da7fe ("mailbox: pcc: Use PCC mailbox channel pointer instead of standard")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/busses/i2c-xgene-slimpro.c

@@ -487,7 +487,7 @@ static int xgene_slimpro_i2c_probe(struct platform_device *pdev)
 		pcc_chan = pcc_mbox_request_channel(cl, ctx->mbox_idx);
 		if (IS_ERR(pcc_chan)) {
 			dev_err(&pdev->dev, "PCC mailbox channel request failed\n");
-			return PTR_ERR(ctx->pcc_chan);
+			return PTR_ERR(pcc_chan);
 		}
 
 		ctx->pcc_chan = pcc_chan;