DMA-API: Fix duplicated word in DMA-API-HOWTO.txt
DMA-API: Fix duplicated word in DMA-API-HOWTO.txt

"coherent" is written twice when it should be just once.

Signed-off-by: Emilio López <86fa523305b8ad6a8a853c04cfef24a0445908d3@elopez.com.ar>
Signed-off-by: Bjorn Helgaas <f10ec01be0c6b54271af5c550cd257810bdf3268@google.com>
KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs