USB: EHCI: export ehci_handshake for ehci-hcd sub-drivers

In order to split ehci-hcd.c into separate modules, handshake() must be
exported. Rename the symbol to add an ehci_ prefix, to avoid any naming
clashes.

Signed-off-by: Manjunath Goudar <manjunath.goudar@linaro.org>
[swarren, split Manjunath's patches more logically, limit this change
to export just handshake()]
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>