erofs: fix fsdax unavailability for chunk-based regular files

erofs: fix fsdax unavailability for chunk-based regular files

DAX can be used to share page cache between VMs, reducing guest memory
overhead. And chunk based data format is widely used for VM and
container image. So enable dax support for it, make erofs better used
for VM scenarios.

Fixes: c5aa903a59db ("erofs: support reading chunk-based uncompressed files")
Signed-off-by: Xin Yin <yinxin.x@bytedance.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20230711062130.7860-1-yinxin.x@bytedance.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>