mips: setup: fix setnocoherentio() boolean setting

Correct a typo/pasto: setnocoherentio() should set
dma_default_coherent to false, not true.

Fixes: 14ac09a6 ("MIPS: refactor the runtime coherent vs noncoherent DMA indicators")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: linux-mips@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>