vfio: revert retry logic for MSI-X BAR mapping

vfio: revert retry logic for MSI-X BAR mapping

This reverts commit d4774a568ba0a5923229974a002972c83eb04570.

The patch is incomplete because kernel 4.16+, while being capable
of mapping MSI-X BARs, will also report if such a capability is
available. Without checking this capability, gratuitous errors
are displayed on kernels <4.16 while VFIO is attempting to mmap
MSI-X BAR and fails, which can be confusing to the user.

Fixes: d4774a568ba0 ("vfio: fix workaround of BAR mapping")

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Acked-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>