usb: dwc3: Add dis_enblslpm_quirk

Add a quirk to clear the GUSB2PHYCFG.ENBLSLPM bit, which controls
whether the PHY receives the suspend signal from the controller.

Cc: <stable@vger.kernel.org> # v3.18+
Signed-off-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 1e276d5..22b47973 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -515,6 +515,9 @@
 	if (dwc->dis_u2_susphy_quirk)
 		reg &= ~DWC3_GUSB2PHYCFG_SUSPHY;
 
+	if (dwc->dis_enblslpm_quirk)
+		reg &= ~DWC3_GUSB2PHYCFG_ENBLSLPM;
+
 	dwc3_writel(dwc->regs, DWC3_GUSB2PHYCFG(0), reg);
 
 	return 0;
@@ -912,6 +915,8 @@
 				"snps,dis_u3_susphy_quirk");
 	dwc->dis_u2_susphy_quirk = device_property_read_bool(dev,
 				"snps,dis_u2_susphy_quirk");
+	dwc->dis_enblslpm_quirk = device_property_read_bool(dev,
+				"snps,dis_enblslpm_quirk");
 
 	dwc->tx_de_emphasis_quirk = device_property_read_bool(dev,
 				"snps,tx_de_emphasis_quirk");
@@ -945,6 +950,7 @@
 		dwc->rx_detect_poll_quirk = pdata->rx_detect_poll_quirk;
 		dwc->dis_u3_susphy_quirk = pdata->dis_u3_susphy_quirk;
 		dwc->dis_u2_susphy_quirk = pdata->dis_u2_susphy_quirk;
+		dwc->dis_enblslpm_quirk = pdata->dis_enblslpm_quirk;
 
 		dwc->tx_de_emphasis_quirk = pdata->tx_de_emphasis_quirk;
 		if (pdata->tx_de_emphasis)