eventdev: negate maintenance capability flag

eventdev: negate maintenance capability flag

Replace RTE_EVENT_DEV_CAP_REQUIRES_MAINT, which signaled the need
for the application to call rte_event_maintain(), with
RTE_EVENT_DEV_CAP_MAINTENANCE_FREE, which does the opposite (i.e.,
signifies that the event device does not require maintenance).

This approach is more in line with how other eventdev hardware and/or
software limitations are handled in the Eventdev API.

Signed-off-by: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
Acked-by: Jerin Jacob <jerinj@marvell.com>