serial/8250: Move UPIO_TSI to powerpc

This iotype is only used by the legacy_serial code in powerpc, so the
code should live there, rather than be compiled in for every 8250
driver.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: linux-serial@vger.kernel.org
Acked-by: David Daney <david.daney@cavium.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>