PCI/IDE: Add IDE establishment helpers

PCI/IDE: Add IDE establishment helpers

There are two components to establishing an encrypted link, provisioning
the stream in Partner Port config-space, and programming the keys into
the link layer via IDE_KM (IDE Key Management). This new library,
drivers/pci/ide.c, enables the former. IDE_KM, via a TSM low-level
driver, is saved for later.

With the platform TSM implementations of SEV-TIO and TDX Connect in mind
this library abstracts small differences in those implementations. For
example, TDX Connect handles Root Port register setup while SEV-TIO
expects System Software to update the Root Port registers. This is the
rationale for fine-grained 'setup' + 'enable' verbs.

The other design detail for TSM-coordinated IDE establishment is that
the TSM may manage allocation of Stream IDs, this is why the Stream ID
value is passed in to pci_ide_stream_setup().

The flow is:

pci_ide_stream_alloc():
    Allocate a Selective IDE Stream Register Block in each Partner Port
    (Endpoint + Root Port), and reserve a host bridge / platform stream
    slot. Gather Partner Port specific stream settings like Requester ID.

pci_ide_stream_register():
    Publish the stream in sysfs after allocating a Stream ID. In the TSM
    case the TSM allocates the Stream ID for the Partner Port pair.

pci_ide_stream_setup():
    Program the stream settings to a Partner Port. Caller is responsible
    for optionally calling this for the Root Port as well if the TSM
    implementation requires it.

pci_ide_stream_enable():
    Enable the stream after IDE_KM.

In support of system administrators auditing where platform, Root Port,
and Endpoint IDE stream resources are being spent, the allocated stream
is reflected as a symlink from the host bridge to the endpoint with the
name:

    stream%d.%d.%d

Where the tuple of integers reflects the allocated platform, Root Port,
and Endpoint stream index (Selective IDE Stream Register Block) values.

Thanks to Wu Hao for a draft implementation of this infrastructure.

Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Lukas Wunner <lukas@wunner.de>
Cc: Samuel Ortiz <sameo@rivosinc.com>
Co-developed-by: Alexey Kardashevskiy <aik@amd.com>
Signed-off-by: Alexey Kardashevskiy <aik@amd.com>
Co-developed-by: Xu Yilun <yilun.xu@linux.intel.com>
Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Link: https://patch.msgid.link/20251031212902.2256310-8-dan.j.williams@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>