Added tests for full coverage of the FPU result sign module

Created by: Dygore

Added two tests to the fpu.s test file to get full coverage for the result sign module.

First I added a test with an infinity FP value as one of the addends which added coverage for most of the unit.

Then I added a test to add coverage for the fmaAs for Z sign bit on the addend of the FMA which I made subtract to make the bit 1.

These tests took the result sign module from 71.19% covered to 100% covered!