i2c: imx: Fix inconsistent IS_ERR and PTR_ERR in i2c_imx_dma_request()

Change the call to PTR_ERR to access the value just tested by IS_ERR.

Fixes: 5b3a23a3 ("i2c: imx: notify about real errors on dma i2c_imx_dma_request")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Esben Haabendal <esben@haabendal.dk>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>