This reverts commit d4774a568b.
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: d4774a568b ("vfio: fix workaround of BAR mapping")
Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Acked-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>
45fdc3ed87