Tegra XUSB host, device mode driver requires the USB 3 companion port
number for corresponding USB 2 port. Add API to retrieve the same.

Signed-off-by: Nagarjuna Kristam <redacted>
Reviewed-by: JC Kuo <jckuo@nvidia.com>
---
V3:
 - Added Reviewed-by updates to commit message.
---
V2:
 - Added -ENODEV as return instead of -1, to sync other errors.
---
 drivers/phy/tegra/xusb.c       | 21 +++++++++++++++++++++
 include/linux/phy/tegra/xusb.h |  2 ++
 2 files changed, 23 insertions(+)

diff --git a/drivers/phy/tegra/xusb.c b/drivers/phy/tegra/xusb.c
index 536b2fc..80dbc57 100644
--- a/drivers/phy/tegra/xusb.c
+++ b/drivers/phy/tegra/xusb.c

@@ -1274,6 +1274,27 @@ int tegra_phy_xusb_utmi_port_reset(struct phy *phy)
 }
 EXPORT_SYMBOL_GPL(tegra_phy_xusb_utmi_port_reset);
 
+int tegra_xusb_padctl_get_usb3_companion(struct tegra_xusb_padctl *padctl,
+				    unsigned int port)
+{
+	struct tegra_xusb_usb2_port *usb2 = tegra_xusb_find_usb2_port(padctl,
+								      port);