The Canon 77D has a burst shooting rate of 6fps and Canon 80D, 7 fps. Knowing fully well the fps is dependent on the camera body, is it possible to increase the fps at least by a single point by software/firmware changes (like "overclocking" of CPU)?
Maybe. Maybe not.
Frame rates in some cameras can be "throttled" somewhat. This allows camera makers to use common parts for models with performance that is differentiated by price in their product lines. But other cameras can also already be at the hardware limits of the motors moving things such as mirrors and shutter curtains.
In the first case it might be possible, but I've never heard of anyone actually trying to do it. As much work as has been done by the folks at Magic Lantern, one would think that if this were even remotely practical someone would have done it for one of the Canon models supported by MAgic Lantern.
You'd need to write your own complete firmware to replace Canon's. Even if you do have such programming skills, along with the ability to crack the current firmware, the time investment needed to do it would likely far outweigh the current $250 difference between the price of the 80D and The 77D. Not to mention that one single mistake could irrevocably brick the camera in question.
Beyond that, max frame rates are a little overly optimistic anyway. To get the maximum frame rate out of any DSLR, one needs to turn off AF, set ISO, Tv, and Av manually, turn off any lens correction, turn off things such as 'Highlight Tone Priority' and 'Auto Lighting Optimizer', etc. Some testers go so far as to test all cameras for max frame rate with the lens cap on to reduce the amount of variety in the recorded frame which makes processing and compression easier.