mackerel: fix minor bug that prevented changing the device prefix for the new shift driver
mackerel: fix minor bug that prevented changing the device prefix for the new shift driver

mslovy/barrelfish,8l/barrelfish,BarrelfishOS/barrelfish,BarrelfishOS/barrelfish,linusyang/barrelfish,BarrelfishOS/barrelfish,kishoredbn/barrelfish,utsav2601/cmpe295A,utsav2601/cmpe295A,utsav2601/cmpe295A,BarrelfishOS/barrelfish,8l/barrelfish,BarrelfishOS/barrelfish,linusyang/barrelfish,utsav2601/cmpe295A,kishoredbn/barrelfish,BarrelfishOS/barrelfish,utsav2601/cmpe295A,8l/barrelfish,BarrelfishOS/barrelfish,mslovy/barrelfish,mslovy/barrelfish,kishoredbn/barrelfish,utsav2601/cmpe295A,mslovy/barrelfish,linusyang/barrelfish,kishoredbn/barrelfish,BarrelfishOS/barrelfish,mslovy/barrelfish,8l/barrelfish,linusyang/barrelfish,mslovy/barrelfish,8l/barrelfish,linusyang/barrelfish,8l/barrelfish,kishoredbn/barrelfish,kishoredbn/barrelfish,BarrelfishOS/barrelfish