mavlink-core: src: Fix embedded v2 read header #518

Job	Run time
mavlink-dump	51s
linting	1m 38s
internal-tests (ardupilotmega)	1m 6s
formatting	8s
internal-tests (asluav)	1m 28s
internal-tests (matrixpilot)	1m 24s
msrv	4m 26s
internal-tests (minimal)	1m 11s
internal-tests (paparazzi)	1m 13s
internal-tests (python_array_test)	1m 17s
internal-tests (slugs)	1m 7s
internal-tests (standard)	1m 12s
internal-tests (test)	1m 1s
internal-tests (ualberta)	1m 20s
internal-tests (uavionix)	1m 4s
internal-tests (icarous)	1m 17s
internal-tests (common)	1m 5s
docs	31s
build (macos-latest, x86_64-apple-darwin, --features ardupilotmega)	1m 29s
build (ubuntu-latest, arm-unknown-linux-musleabihf, --features ardupilotmega)	1m 55s
build (ubuntu-latest, armv7-unknown-linux-musleabihf, --features ardupilotmega)	2m 5s
build (ubuntu-latest, x86_64-unknown-linux-musl, --features ardupilotmega)	1m 58s
build (ubuntu-latest, x86_64-unknown-linux-musl, --features ardupilotmega,emit-description,emit-e...	2m 1s
build (ubuntu-latest, thumbv7m-none-eabi, --no-default-features --features embedded)	1m 10s
build (windows-latest, x86_64-pc-windows-msvc, --features ardupilotmega)	3m 12s
test-embedded-size	40s
	37m 49s

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