usb: dwc3: add Tx de-emphasis quirk

This patch adds Tx de-emphasis quirk, and the Tx de-emphasis value is
configurable according to PIPE3 specification.

Value		Description
0		-6dB de-emphasis
1		-3.5dB de-emphasis
2		No de-emphasis
3		Reserved

It can be configured on DT or platform data.

Signed-off-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/dwc3/platform_data.h b/drivers/usb/dwc3/platform_data.h
index 4a0f06b..e1ab900 100644
--- a/drivers/usb/dwc3/platform_data.h
+++ b/drivers/usb/dwc3/platform_data.h
@@ -36,4 +36,7 @@
 	unsigned del_phy_power_chg_quirk:1;
 	unsigned lfps_filter_quirk:1;
 	unsigned rx_detect_poll_quirk:1;
+
+	unsigned tx_de_emphasis_quirk:1;
+	unsigned tx_de_emphasis:2;
 };