Config: Add "DSP" to GetINIToSectionMap

The "DSP" game INI section name was supported by BootManager.cpp
before the section was ported to the new config system.
For backwards compatibility, we should keep supporting it.

Should fix https://bugs.dolphin-emu.org/issues/12792

Source/Core/Core/ConfigLoaders/GameConfigLoader.cpp

@@ -90,6 +90,7 @@ static const INIToSectionMap& GetINIToSectionMap()
 {
   static const INIToSectionMap ini_to_section = {
       {"Core", {Config::System::Main, "Core"}},
+      {"DSP", {Config::System::Main, "DSP"}},
       {"Display", {Config::System::Main, "Display"}},
       {"Video_Hardware", {Config::System::GFX, "Hardware"}},
       {"Video_Settings", {Config::System::GFX, "Settings"}},