vfio: Use kconfig if XX/endif blocks instead of repeating 'depends on'

vfio: Use kconfig if XX/endif blocks instead of repeating 'depends on'

This results in less kconfig wordage and a simpler understanding of the
required "depends on" to create the menu structure.

The next patch increases the nesting level a lot so this is a nice
preparatory simplification.

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/20210826103912.128972-13-yishaih@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>