ARM: pxa/eseries: switch to using gpio-vbus transceiver

Switch from handling gpio-vbus in pxa25x_udc to using standard gpio-vbus
tranceiver.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: Ian Molton <spyro@f2s.com>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>