net: irda: pxaficp_ir: convert to readl and writel

Convert the pxa IRDA driver to readl and writel primitives, and remove
another set of direct registers access. This leaves only the DMA
registers access, which will be dealt with dmaengine conversion.
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Tested-by: Petr Cvek <petr.cvek@tul.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>