Centralize compiler macros in a top-level package

There is at least one instance of a compiler macro in CORE-V-MCU that is defined and used in disjointed parts of the RTL. The macro in question is USE_FPU. It is used in fc_subsystem.sv to set the FPU parameter for the CV32E40P core. The macro is defined in pulp_soc_defines.sv. This is a dangerous situation because the value of USE_FPU passed to the core is dependent on compile order:

• if pulp_soc_defines.sv is compiled before fc_subsystem.sv then USE_FPU is 1.
• if fc_subsystem.sv is compiled before pulp_soc_defines.sv then USE_FPU is undefined.

At a minimum, the above situation must be resolved. It would also be a great idea to review all macros in the MCU and ensure that either the macros are defined in a top-level package or define in the module in which they are used. @gmartin102, I am assigning this to you as you are the default RTL engineer on this project. Feel free to delegate.