[COMMANDS] vfs: Add 'host_load_list' and 'guest_load_list' sub-commands

Quite often we would frequently load multiple files for host or guest
hence having sub-commands to pick-up list of files to be loaded from
text file can be quite useful.

This patch adds sub-commands 'host_load_list' and 'guest_load_list'
for the above purpose.

Signed-off-by: Anup Patel <anup@brainfault.org>