I did check in menuconfig, and loadable module support was builtin. I assume that this means that I should not have received the error that I had.
I was able to get past that build error, though another error came up that seems to be unrelated to the first error. It looks like this driver that I was building may not have been developed very well, or maybe it was developed for a different kernel configuration.
1) is there a command line command that will tell me if modules are enabled?
2) where is there more documentation on "menuconfig" and its various options (are these unique to a particular kernel version)?