ARM: OMAP: Fix DMA channel irq handling for omap24xx

- DMA CSR register is cleared by reading on omap1, but on
  omap2 it is cleard by writing to it.

- DMA TOUT interrupt does not exist on omap24xx, rename it

- Add SECURE and MISALIGNED errors by default for omap24xx

- Add defines for external DMA request lines

Signed-off-by: Tony Lindgren <tony@atomide.com>