Initial (non-working) commit of new mixer HDL
Renamed coeff to param to match assembler
Changed instruction memory interface to simple instruction input port (assumes PC is external to dsp_core)
Removed most references to offset
changed instruction internals (including adding opcodes in current assembler)
remove instruction decode and just pipeline instruction word itself
Remove program counter (now external to dsp_core)
Added opcode decoding; also fixed some little things (leftover PCs), did a little renaming, and removed the instruction input in top.sv so it synthesizes
added more reset logic
added inter-core bus output in writeback stage