multiboot2: add missing tags #1027

Job	Run time
build (msrv) / rust	18s
build (nightly) / rust	17s
build (stable) / rust	16s
build no_std (stable) [Windows] / rust	1m 19s
build no_std (stable) / rust	18s
build no_std (stable) [w/o builder] / rust	11s
style (stable) / rust	13s
tests with miri (nightly) / rust	1m 22s
style (nightly) / rust	27s
build no_std (nightly) / rust	19s
style (msrv) / rust	18s
build no_std (msrv) / rust	18s
	5m 36s

Provide feedback