exfat kernel support missing under Heads

[tlaurion]

extfat support would ease initial OS installation and boot media preparation.

Since fat32 is limiting files <4gb, formatting into NTFS would be wrong, and formatting into ext3/ext4 is not necessarily easy for some users/from some OSes, that thumb drives and sdcards normally come per-formatted with exfat, it would be animprovement if newcomers could simply drop ISOs+iso.asc/iso.sig and boot directly to already preformatted exfat bought external removable devices.

Let's remember that on a fresh externally flashed Heads firmware, Heads on initial boot picks up and detects that no OS is installed on internal hard drive and now propose to boot from USB. It would be nice to ease things a little further and permit users to just drop iso and iso.asc/iso.sig files (distribution provided detached signatures) on an already formatted exfat drive from a second computer, not trusting it, knowing that Heads will prevent booting from a corrupted/tampered with ISO.

[tlaurion]

Requires kernel version bump (exfat not under 4.14.4).