vfio: Use select for eventfd

If VFIO_VIRQFD is required then turn on eventfd automatically.
The majority of kconfig users of the EVENTFD use select not depends on.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
Link: https://lore.kernel.org/r/20210826103912.128972-12-yishaih@nvidia.com


Signed-off-by: Alex Williamson <alex.williamson@redhat.com>