Don't create extra /usr partition if using verity
Closes
# <file system> <dir> <type> <options> <makeimg agrs>
LABEL=EFI /boot/efi vfat umask=0077 type=uefi
-LABEL=ROOT / ext4 rw,errors=remount-ro,prjquota,discard verity
-LABEL=USR /usr ext4 ro,discard verity
+LABEL=ROOT / ext4 ro verity
LABEL=OVERLAY /overlay ext4 rw,discard size=512MiB
