vfio/mdev: Fix missing static's on MDEV_TYPE_ATTR's

vfio/mdev: Fix missing static's on MDEV_TYPE_ATTR's

These should always be prefixed with static, otherwise compilation
will fail on non-modular builds with

ld: samples/vfio-mdev/mbochs.o:(.data+0x2e0): multiple definition of `mdev_type_attr_name'; samples/vfio-mdev/mdpy.o:(.data+0x240): first defined here

Fixes: 73831c8dd461 ("sample: vfio bochs vbe display (host device for bochs-drm)")
Fixes: 03b85fd75ff1 ("sample: vfio mdev display - host device")
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Message-Id: <1-v2-d36939638fc6+d54-vfio2_jgg@nvidia.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>