Clarify license terms for n64.ld

[fsomers]

(follow-on from DMs with rasky)

I authored the original version of n64.ld, a ...long... time ago.

There was no licence file distributed with the original "release", and at the time I was not concerned with license terms - it was meant to be in a similar spirit to the goals for libdragon - note the following extract from the start of the readme.txt that was part of the original release:

So you want to code for the N64.... 
And you've been looking for a legitimate and freely available development system you could use... 
We did... We've put together one, and here it is!

I am completely fine with stating that any g0dev parts which may remain (noting the original version of n64.ld) can be included and treated as though they are unencumbered, and can be licensed under this project's license: https://github.com/DragonMinded/libdragon/blob/trunk/LICENSE.md

[rasky]

Thanks @fsomers, much appreciated! I will now clarify the license terms in the file.