serial: 8250_dw: Do not use readl/writel before checking port iotype

Direct call to readl()/writel() is checked against iotype
and in case of UPIO_MEM32BE we use ioread32be()/iowrite32be()
instead of them.

Signed-off-by: Noam Camus <noamc@ezchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>