interrupts: add allocator and accessors

interrupts: add allocator and accessors

Prototype/Implement get set APIs for interrupt handle fields.
User won't be able to access any of the interrupt handle fields
directly while should use these get/set APIs to access/manipulate
them.

Internal interrupt header i.e. rte_eal_interrupt.h is rearranged,
as APIs defined are moved to rte_interrupts.h and epoll specific
definitions are moved to a new header rte_epoll.h.
Later in the series rte_eal_interrupt.h will be removed.

Signed-off-by: Harman Kalra <hkalra@marvell.com>
Acked-by: Ray Kinsella <mdr@ashroe.eu>
Acked-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
Signed-off-by: David Marchand <david.marchand@redhat.com>
Tested-by: Raslan Darawsheh <rasland@nvidia.com>