blkin: Endpoint inherits blkin_endpoint
blkin: Endpoint inherits blkin_endpoint

this allows Trace to pass Endpoint* directly to the c interface, rather
than calling Endpoint->get_blkin_ep()

Signed-off-by: Casey Bodley <77bc9a9984e6786c5799d7a71768cf023120ef76@cohortfs.com>

linuxbox2/blkin,linuxbox2/blkin,linuxbox2/blkin