How did you set it to “m”? Was it through something like “make menuconfig”? Or was it editing “.config” directly? If the former, then this is ok; if the latter, then you can’t do that.
If it turns out this can be built as a module, then logs are needed to know more about what went wrong. Normally you would get symbol errors if you add a feature which depends on another feature, and that other feature is not present…in theory this won’t happen if you use something like “make menuconfig”. Note that if this is the reason for a symbol failure, then this will fail either integrated or in module format…being a module or not won’t change what other features were selected (except if “make menuconfig” is used it might automatically add the related features).
Another reason for a symbol error is if you’ve compiled code from one kernel version and try to run it in another version.
The easiest place to start is to know what your starting configuration was, and then whether you modified it via “make menuconfig” or via direct edit of “.config”. How did your configuration start, and how did you edit this?