nvdec: Tidy up header includes

Prevents a few unnecessary inclusions.

src/video_core/command_classes/vic.cpp

@@ -26,7 +26,7 @@ void Vic::VicStateWrite(u32 offset, u32 arguments) {
     std::memcpy(state_offset, &arguments, sizeof(u32));
 }
 
-void Vic::ProcessMethod(Vic::Method method, const std::vector<u32>& arguments) {
+void Vic::ProcessMethod(Method method, const std::vector<u32>& arguments) {
     LOG_DEBUG(HW_GPU, "Vic method 0x{:X}", static_cast<u32>(method));
     VicStateWrite(static_cast<u32>(method), arguments[0]);
     const u64 arg = static_cast<u64>(arguments[0]) << 8;