Regression from commit:
loader/linux: do not pad initrd with zeroes at the end
a8c473288d3f0a5e17a903a5121dea1a695dda3b
Wimboot fails since the change above because it expects the "trailer"
initrd element on an aligned address.
This issue shows only when newc_name is used and the last initrd
entry has a not aligned size.