USB: s3c2410_udc: Add common implementation for GPIO controlled pullups

Currently all boards using the s3c2410_udc driver use a GPIO to control the
state of the pullup, as a result the same code is reimplemented in each board
file.
This patch adds support for using a GPIO to control the pullup state to the udc
driver, so the boards can use a common implementation.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>