pds_vdpa: protect Makefile from unconfigured debugfs

debugfs.h protects itself from an undefined DEBUG_FS, so it is
not necessary to check it in the driver code or the Makefile.
The driver code had been updated for this, but the Makefile had
missed the update.

Link: https://lore.kernel.org/linux-next/fec68c3c-8249-7af4-5390-0495386a76f9@infradead.org/


Fixes: a16291b5 ("pds_vdpa: Add new vDPA driver for AMD/Pensando DSC")
Signed-off-by: Shannon Nelson <shannon.nelson@amd.com>
Message-Id: <20230706231718.54198-1-shannon.nelson@amd.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Acked-by: Jason Wang <jasowang@redhat.com>