virtio-blk: remove unneeded "likely" statements

Usually we use "likely/unlikely" to optimize the fast path. Remove
redundant "likely/unlikely" statements in the control path to simplify
the code and make it easier to read.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Link: https://lore.kernel.org/r/20210905085717.7427-1-mgurtovoy@nvidia.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Chaitanya Kulkarni <ckulkarnilinux@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>