tools/create-image.sh: add linux-firmware package by default

Multiple usb drivers (among others) are missing firmware thus
stopping short any probe() attempts.

A couple examples are:
1) comedi usb drivers: usbdux, usbduxfast etc.
2) drivers/media/usb/{s2255,go7007}
and a few others at the very least.

Add the required module 'firmware-linux' (carries both free and
nonfree batches of built firmware) to the list of default packages.

This is not an ideal solution considering the goal of a *minimal*
distribution. Still, this will increase code coverage.

Author: fellair

tools/create-image.sh

@@ -7,7 +7,7 @@
 set -eux
 
 # Create a minimal Debian distribution in a directory.
-PREINSTALL_PKGS=openssh-server,curl,tar,gcc,libc6-dev,time,strace,sudo,less,psmisc,selinux-utils,policycoreutils,checkpolicy,selinux-policy-default,firmware-atheros,debian-ports-archive-keyring
+PREINSTALL_PKGS=openssh-server,curl,tar,gcc,libc6-dev,time,strace,sudo,less,psmisc,selinux-utils,policycoreutils,checkpolicy,selinux-policy-default,firmware-atheros,firmware-linux,debian-ports-archive-keyring
 
 # If ADD_PACKAGE is not defined as an external environment variable, use our default packages
 if [ -z ${ADD_PACKAGE+x} ]; then