Handle the following EXT4 incompatible features:
EXT4_FEATURE_INCOMPAT_MMP (Multi-Mount Protection)
Prevents multiple read-write mounts of the same filesystem.
Since grub2-bhyve mounts filesystems read-only, it is safe to ignore.
EXT4_FEATURE_INCOMPAT_CSUM_SEED
Allows tools such as tune2fs to change the UUID on a mounted
metadata-checksummed filesystem. Safe to ignore because the
driver does not perform checksum verification.
EXT4_FEATURE_INCOMPAT_LARGEDIR
Enables directories larger than 2GB and 3-level htrees.
Safe to ignore because the GRUB ext2 driver does not implement
DIR_INDEX.
This patch mirrors upstream behavior. It unblocks booting from
distributions such as Alpine Linux.