usb: dwc3: make HIRD threshold configurable

HIRD threshold should be configurable by different platforms.

From DesignWare databook:
When HIRD_Threshold[4] is set to 1b1 and HIRD value is greater than or
equal to the value in HIRD_Threshold[3:0], dwc3 asserts output signals
utmi_l1_suspend_n to put PHY into Deep Low-Power mode in L1.

When HIRD_Threshold[4] is set to 1b0 or the HIRD value is less than
HIRD_Threshold[3:0], dwc3 asserts output signals utmi_sleep_n on L1.

Signed-off-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 88a065f..398c12f 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -2295,11 +2295,7 @@
 		reg = dwc3_readl(dwc->regs, DWC3_DCTL);
 		reg &= ~(DWC3_DCTL_HIRD_THRES_MASK | DWC3_DCTL_L1_HIBER_EN);
 
-		/*
-		 * TODO: This should be configurable. For now using
-		 * maximum allowed HIRD threshold value of 0b1100
-		 */
-		reg |= DWC3_DCTL_HIRD_THRES(12);
+		reg |= DWC3_DCTL_HIRD_THRES(dwc->hird_threshold);
 
 		/*
 		 * When dwc3 revisions >= 2.40a, LPM Erratum is enabled and