ARM: tegra: export usb phy symbols

The ehci driver can be a module, so the functions provided
by the tegra platform code used by ehci-tegra need to
be exported.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Alan Ott <alan@signal11.us>
Signed-off-by: Olof Johansson <olof@lixom.net>