staging/fwserial: Assume firmware is OHCI-complaint

Devices which are OHCI v1.0/ v1.1/ v1.2-draft compliant or
RFC 2734 compliant are required by specification to support
max_rec of 8 (512 bytes) or more. Accept reported value.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>