Well, first I wanted to check is it really is an issue of the missing firmware, so I've only supplied you with the command to do it on the fly. Now that we know that the firmware lack was the issue, we can make it persist.
First of all: I don't have any Sparky installation with me (I'm at work right now, but occasionally check the forums), so I'm going to try telling you what to do from memory (you need to be root).
1. Locate the modules directory in /etc (it's either /etc/modules or /etc/modules.d - it must be an already existing directory, as we don't want to touch the main configuration file and creating it might now work).
2. When you're in the directory stated above just type:
echo brcmsmac > broadcom
(It's doesn't have to be "broadcom", you can name it as you like).
It's a module start-up loading configuration. If you need any module loaded at boot time you just place a file with the module's name there (or in a /etc/modules.conf file if one exists - but that's discouraged, as the /etc/modules.d directory is a better choice and you have the certainty that running an upgrade won't override your configuration). That should get you a working connection on startup.