WPC: remove (again) snd FIRQ as it is not wired #1295

Job	Run time
Version	5s
Build libpinmame-win-x64	2m 40s
Build libpinmame-win-x86	2m 10s
Build libpinmame-win-arm64	1m 55s
Build libpinmame-osx-x64	2m 28s
Build libpinmame-osx-arm64	1m 38s
Build libpinmame-ios-arm64	1m 4s
Build libpinmame-tvos-arm64	1m 2s
Build libpinmame-linux-x64	3m 7s
Build libpinmame-android-arm64-v8a	1m 34s
Build libpinmame-osx	8s
dispatch	0s
	17m 51s

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