FAT32 limits for file count and file name lengths

[jonashoechst]

The limitations on FAT32 are high rather fast in our use cases, esp. when recording audio / guano files. In one test that was reached over the course of a weekend:

pi at ops-prototyp-mntr in / 
$ ls data/ops-prototyp-mntr/soundscapepipe/ | wc -l
12742

More on file limits here: https://stackoverflow.com/questions/37135262/fat32-number-of-files-per-directory-limit

[jonashoechst]

exFAT does not have these limitations (and we use it for mmcblk2 / internal storage) but is not regularly shipped on flash drives.

tsOS-base/usr/share/initramfs-tools/scripts/local-premount/firstboot

Lines 69 to 71 in 7455d83

	DATA_DEV_NAME=$(lsblk -no kname "$ROOT_DEV" | tail -1)
	DATA_DEV="/dev/$DATA_DEV_NAME"
	mkfs.exfat -n datafs "$DATA_DEV"