serial: 8250: remove a few lines of dead code

Support for the WindRiver SBC8560 board was removed in v3.6. But there
are still a few lines depending on its obsolete Kconfig macro. Remove
these now.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>