USB: isp1760: use __devexit_p() for remove function

The isp1760_plat_remove function is declared with __devexit, so the
.remove assignment needs to be wrapped with __devexit_p().

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>