usb: of: fix build breakage caused by recent patches

commit 052a11d (usb: phy: make PHY driver selection
possible by controller drivers) changed the rules
on how drivers/usb/phy/of.c would be compiled and
failed to update include/linux/usb/of.h accordingly.

Because of that, we can fall into situations where
of_usb_get_phy_mode() is redefined. In order to fix
the error, we update the IS_ENABLED() check in
include/linux/usb/of.h to reflect the condition
where of.c is built.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Felipe Balbi <balbi@ti.com>

include/linux/usb/of.h

@@ -27,7 +27,7 @@ of_usb_get_maximum_speed(struct device_node *np)
 }
 #endif
 
-#if IS_ENABLED(CONFIG_OF) && IS_ENABLED(CONFIG_USB_PHY)
+#if IS_ENABLED(CONFIG_OF) && IS_ENABLED(CONFIG_USB_SUPPORT)
 enum usb_phy_interface of_usb_get_phy_mode(struct device_node *np);
 #else
 static inline enum usb_phy_interface of_usb_get_phy_mode(struct device_node *np)