nvmet: Add support for I/O queue management admin commands

The I/O submission queue management admin commands
(nvme_admin_delete_sq, nvme_admin_create_sq, nvme_admin_delete_cq,
and nvme_admin_create_cq) are mandatory admin commands for I/O
controllers using the PCI transport, that is, support for these commands
is mandatory for a a PCI target I/O controller.

Implement support for these commands by adding the functions
nvmet_execute_delete_sq(), nvmet_execute_create_sq(),
nvmet_execute_delete_cq() and nvmet_execute_create_cq() to set as the
execute method of requests for these commands. These functions will
return an invalid opcode error for any controller that is not a PCI
target controller. Support for the I/O queue management commands is also
reported in the command effect log  of PCI target controllers (using
nvmet_get_cmd_effects_admin()).

Each management command is backed by a controller fabric operation
that can be defined by a PCI target controller driver to setup I/O
queues using nvmet_sq_create() and nvmet_cq_create() or delete I/O
queues using nvmet_sq_destroy().

As noted in a comment in nvmet_execute_create_sq(), we do not yet
support sharing a single CQ between multiple SQs.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Rick Wertenbroek <rick.wertenbroek@gmail.com>
Tested-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Keith Busch <kbusch@kernel.org>