shader_ir: Pass decoded nodes as a whole instead of per basic blocks

Some games call LDG at the top of a basic block, making the tracking
heuristic to fail. This commit lets the heuristic the decoded nodes as a
whole instead of per basic blocks.

This may lead to some false positives but allows it the heuristic to
track cases it previously couldn't.

src/video_core/shader/decode/ffma.cpp

@@ -12,7 +12,7 @@ namespace VideoCommon::Shader {
 using Tegra::Shader::Instruction;
 using Tegra::Shader::OpCode;
 
-u32 ShaderIR::DecodeFfma(BasicBlock& bb, const BasicBlock& code, u32 pc) {
+u32 ShaderIR::DecodeFfma(BasicBlock& bb, u32 pc) {
     const Instruction instr = {program_code[pc]};
     const auto opcode = OpCode::Decode(instr);