eal/linux: add interrupt API for drivers

eal/linux: add interrupt API for drivers

The patch exposes intr event fd create and release for PMD.
The device driver can assign the number of event associated with interrupt vector.
It also provides misc functions to check 1) allows other slowpath intr(e.g. lsc);
2) intr event on fastpath is enabled or not.

Signed-off-by: Cunming Liang <cunming.liang@intel.com>