Remove exfat utf8 quirk flag. Add more options to vfat.

I'm using exfat rev 1691cda, syslog says: `kernel: [EXFAT] Unrecognized
mount option utf8 or missing value` .

According to Archlinux fstab wikipage:

    flush - The vfat option to flush data more often, thus making copy dialogs or progress bars to stay up until all data is written.