initramfs-tools MODULES=dep default on ARM

Frans Pop reported recently that the initramfs did not fit in the flash of the QNAP TS-109 when you used LVM. We had problems with initramfs images that were too large before (on the NSLU2). By default, initramfs-tools uses the MODULES=most setting which puts all modules that might be of interest to booting a machine in the initramfs. This is a good idea on a PC where the hardware can change a lot, but it makes less sense on most NAS devices.

Frans has now changed debian-installer so the MODULES policy can be chosen during the installation. His change allowed architecture specific defaults, so I've changed ARM to use MODULES=dep. debian-installer will now create the file /etc/initramfs-tools/conf.d/driver-policy with a MODULES setting that will override that from /etc/initramfs-tools/initramfs.conf. On QNAP devices, I intend to only support MODULES=dep installations, so please change your configuration if you've installed Debian already. On the NSLU2, MODULES=most will of course continue to be supported.