USB: renesas_usbhs: drop unused legacy-phy support

Drop support for legacy phys for rcar2 which hasn't been used with a
mainline kernel since commit 9080b8dc ("ARM: OMAP2+: Remove legacy
usb-host.c platform init code"). Specifically, since that commit
usb_get_phy_dev() have always returned -ENODEV and consequently this
code has not been used.

Note that the legacy-phy API is still being used in gadget mode to bind
the peripheral controller.

Acked-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>