subr_devmap: Implement pmap_mapdev with pmap_mapdev_attr

[andrew]

Summary

We can now support pmap_mapdev_attr on arm. Switch to use this to
implement pmap_mapdev to reduce duplicate code.

Sponsored by: Arm Ltd

[andrew]

Only call devmap_ptov for device mappings

[mmel]

sys/kern/subr_devmap.c

266

I'm afraid that multiple mappings of the same page with different cache or type properties leads to undefined behavior on most (if not all) architectures. In this case, I don't see a solution other than panic().

[andrew]

KASSERT ma == VM_MEMATTR_DEVICE

[mmel]

Thanks