nitro_enclaves: Init PCI device driver

nitro_enclaves: Init PCI device driver

The Nitro Enclaves PCI device is used by the kernel driver as a means of
communication with the hypervisor on the host where the primary VM and
the enclaves run. It handles requests with regard to enclave lifetime.

Setup the PCI device driver and add support for MSI-X interrupts.

Changelog

v9 -> v10

* Update commit message to include the changelog before the SoB tag(s).

v8 -> v9

* Init the reference to the ne_pci_dev in the ne_devs data structure.

v7 -> v8

* Add NE PCI driver shutdown logic.

v6 -> v7

* No changes.

v5 -> v6

* Update documentation to kernel-doc format.

v4 -> v5

* Remove sanity checks for situations that shouldn't happen, only if
  buggy system or broken logic at all.

v3 -> v4

* Use dev_err instead of custom NE log pattern.
* Update NE PCI driver name to "nitro_enclaves".

v2 -> v3

* Remove the GPL additional wording as SPDX-License-Identifier is
  already in place.
* Remove the WARN_ON calls.
* Remove linux/bug include that is not needed.
* Update static calls sanity checks.
* Remove "ratelimited" from the logs that are not in the ioctl call
  paths.
* Update kzfree() calls to kfree().

v1 -> v2

* Add log pattern for NE.
* Update PCI device setup functions to receive PCI device data structure and
  then get private data from it inside the functions logic.
* Remove the BUG_ON calls.
* Add teardown function for MSI-X setup.
* Update goto labels to match their purpose.
* Implement TODO for NE PCI device disable state check.
* Update function name for NE PCI device probe / remove.

Reviewed-by: Alexander Graf <graf@amazon.com>
Signed-off-by: Alexandru-Catalin Vasile <lexnv@amazon.com>
Signed-off-by: Alexandru Ciobotaru <alcioa@amazon.com>
Signed-off-by: Andra Paraschiv <andraprs@amazon.com>
Link: https://lore.kernel.org/r/20200921121732.44291-5-andraprs@amazon.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>