MIPS: Octeon: remove mips dma-default stubs

MIPS: Octeon: remove mips dma-default stubs

Octeon doesn't use the dma-default code, and now doesn't built it either,
so these stubs can be removed.

Signed-off-by: Christoph Hellwig <[email protected]>
Patchwork: https://patchwork.linux-mips.org/patch/19537/
Signed-off-by: Paul Burton <[email protected]>
Cc: Florian Fainelli <[email protected]>
Cc: David Daney <[email protected]>
Cc: Kevin Cernekee <[email protected]>
Cc: Jiaxun Yang <[email protected]>
Cc: Tom Bogendoerfer <[email protected]>
Cc: Huacai Chen <[email protected]>
Cc: [email protected]
Cc: [email protected]