MX28: SPI: Pull out the PIO transfer function

Pull out all the PIO transfer logic into separate function,
so DMA can be added.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Otavio Salvador <otavio@ossystems.com.br>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Wolfgang Denk <wd@denx.de>
1 file changed