mkinitramfs: Warn if initrd size > some ratio of RAM size
On boards with small RAM size (512MB for example), depending on which packages are installed, the initrd size can be so big that the system silently fails to boot: simply warn the user that it could happen.
The 60% ratio was set arbitrarily to catch the problem on the board I was working on.
Signed-off-by: Alexandre Ghiti alexandre.ghiti@canonical.com