[PATCH 4/7] dma-mapping: Always provide dma_default_coherent

[Jiaxun Yang]

> 2023年2月21日 17:58，Christoph Hellwig <hch at lst.de> 写道：
> 
> On Tue, Feb 21, 2023 at 12:46:10PM +0000, Jiaxun Yang wrote:
>> dma_default_coherent can be useful for determine default coherency
>> even on arches without noncoherent support.
> 
> How?

I just want to make this symbol always available so OF code can reference it on all arches.