UBUNTU: Add 3 missing files to prerm remove file list

BugLink: http://bugs.launchpad.net/bugs/345623
BugLink: http://bugs.launchpad.net/bugs/415832

While purging some old kernels, Matt noticed warnings from dpkg
that it was not removing /lib/modules/xxx. "modules.alias.bin modules.dep.bin
modules.symbols.bin" 3 files are left behind. The new files are the result
of changes to the modules-tools-init package, e.g., modprobe and depmod now
create and use a binary cache file.

This patch fixes this by adding these 3 files to the prerm remove file list.

Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
Acked-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>

(cherry-picked from 8b453930

 for fsl-imx51)
Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
Signed-off-by: Andy Whitcroft <apw@canonical.com>