usb: isp1760: remove platform data struct and code

Since the removal of the Blackfin port with:
commit 4ba66a97 ("arch: remove blackfin port")

No one is using or referencing this header and platform data struct.
Remove them.

Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Link: https://lore.kernel.org/r/20210513084717.2487366-5-rui.silva@linaro.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>