usb: xhci-mtk: add support optional controller reset

Add support controller reset via a reset-controller usually in infracfg,
it's different with the software reset by IPPC which only used to reset MAC,
and it will also reset IPPC meanwhile.

Reviewed-by: AngeloGioacchino Del Regno <[e-mail]>
Signed-off-by: Chunfeng Yun <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/host/xhci-mtk.c

···
 #include <linux/pm_wakeirq.h>
 #include <linux/regmap.h>
 #include <linux/regulator/consumer.h>
+#include <linux/reset.h>
 
 #include "xhci.h"
 #include "xhci-mtk.h"
···
 	ret = clk_bulk_prepare_enable(BULK_CLKS_NUM, mtk->clks);
 	if (ret)
 		goto disable_ldos;
+
+	ret = device_reset_optional(dev);
+	if (ret) {
+		dev_err_probe(dev, ret, "failed to reset controller\n");
+		goto disable_clk;
+	}
 
 	hcd = usb_create_hcd(driver, dev, dev_name(dev));
 	if (!hcd) {