mxs: dma: Fix APBH DMA driver for MX23

The MX23 has less channels for the APBH DMA, sligtly different register
layout and some bits in those registers are placed differently. Reflect
this in the driver. This patch fixes MMC/DMA issue on MX23.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Otavio Salvador <otavio@ossystems.com.br>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Cc: Stefano Babic <sbabic@denx.de>