* Introduce feature flags which allows the proxy and m1n1 to determine which
features they have in common.
* Add a feature flag that disables checksumming (by replacing checksums with
constant values) for the data packets exchanged by REQ_MEMREAD, REQ_MEMWRITE
and REQ_EVENT. The feature is enabled if m1n1 supports it; checksumming is kept
enabled for UART communication.
* To ensure no packet loss when checksumming is disabled, an extra sentinel
value is added after the exchanged data for memory read/write operations.
Signed-off-by: Vincent Duvert <vincent@duvert.net>
3d1747466b