mmc: dw_mmc: simplify optional reset handling

As of commit bb475230 ("reset: make optional functions really
optional"), the reset framework API calls use NULL pointers to describe
optional, non-present reset controls.

This allows to return errors from devm_reset_control_get_optional and to
call reset_control_(de)assert unconditionally.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Link: https://lore.kernel.org/r/20210305090724.18832-1-p.zabel@pengutronix.deSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/dw_mmc.c

@@ -3093,10 +3093,8 @@ static struct dw_mci_board *dw_mci_parse_dt(struct dw_mci *host)
 
 	/* find reset controller when exist */
 	pdata->rstc = devm_reset_control_get_optional_exclusive(dev, "reset");
-	if (IS_ERR(pdata->rstc)) {
-		if (PTR_ERR(pdata->rstc) == -EPROBE_DEFER)
-			return ERR_PTR(-EPROBE_DEFER);
-	}
+	if (IS_ERR(pdata->rstc))
+		return ERR_CAST(pdata->rstc);
 
 	if (device_property_read_u32(dev, "fifo-depth", &pdata->fifo_depth))
 		dev_info(dev,
@@ -3202,7 +3200,7 @@ int dw_mci_probe(struct dw_mci *host)
 		goto err_clk_ciu;
 	}
 
-	if (!IS_ERR(host->pdata->rstc)) {
+	if (host->pdata->rstc) {
 		reset_control_assert(host->pdata->rstc);
 		usleep_range(10, 50);
 		reset_control_deassert(host->pdata->rstc);
@@ -3342,7 +3340,6 @@ int dw_mci_probe(struct dw_mci *host)
 	if (host->use_dma && host->dma_ops->exit)
 		host->dma_ops->exit(host);
 
-	if (!IS_ERR(host->pdata->rstc))
 	reset_control_assert(host->pdata->rstc);
 
 err_clk_ciu:
@@ -3371,7 +3368,6 @@ void dw_mci_remove(struct dw_mci *host)
 	if (host->use_dma && host->dma_ops->exit)
 		host->dma_ops->exit(host);
 
-	if (!IS_ERR(host->pdata->rstc))
 	reset_control_assert(host->pdata->rstc);
 
 	clk_disable_unprepare(host->ciu_clk);