usb: isp1362: remove blackfin arch glue

The blackfin architecture is getting removed, and this is the last
remaining architecture specific setting, so the various hacks
can be removed now.

From all I can tell, there are no remaining in-tree users of the
driver, but it could be used by out-of-tree platform ports.
I've marked the driver as 'depends on COMPILE_TEST', short of
removing it outright.

It was originally written for some ARM PXA machines using the same
chip, but that platform never really worked and the code has been
removed a long time ago.

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Aaron Wu <aaron.wu@analog.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>