There's a merged pull request on the void-packages repository

zfs: add support for linux5.8
https://github.com/void-linux/void-packages/pull/24242

Description:
Backport an upstream commit to support `__vmalloc` prototype change. Also clean up the `dkms.patch` to avoid `dkms.conf.orig` artifacts from an imperfect match and more intelligently prune patches from the build tree in preparation for packing `clean.tar.gz` for DKMS.

Build and run tested on `linux5.7` and `linux5.8`. There should be no issues with older kernel versions.

@Vaelatern @ericonr @zdykstra