ARM: LPC32xx: Provide DMA filter callbacks via platform data

The SLC and MLC NAND drivers now need their dma_filter callbacks via platform
data to make them independent of single DMA engine drivers.

(This also helps fixing build errors of the SLC and MLC drivers when building
as modules because direct access to AMBA dma filter functions isn't available
via export.)

Signed-off-by: Roland Stigge <stigge@antcom.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>