Only include phydev_if.h when needed

We only need to include phydev_if.h in phy.c when FDT is enabled and
don't need it at all in phy_usb.c.

Sponsored by:	Innovate UK

sys/dev/extres/phy/phy.c

@@ -45,7 +45,9 @@ __FBSDID("$FreeBSD$");
 #include  <dev/extres/phy/phy.h>
 #include  <dev/extres/phy/phy_internal.h>
 
+#ifdef FDT
 #include "phydev_if.h"
+#endif
 
 MALLOC_DEFINE(M_PHY, "phy", "Phy framework");
 

sys/dev/extres/phy/phy_usb.c

@@ -38,8 +38,6 @@ __FBSDID("$FreeBSD$");
 #include <dev/extres/phy/phy_usb.h>
 #include <dev/extres/phy/phy_internal.h>
 
-#include "phydev_if.h"
-
 /*
  * USB phy controller methods.
  */