rust: device: fix broken intra-doc links

rust: device: fix broken intra-doc links

The `pci` module is conditional on CONFIG_PCI. When it's disabled, the
intra-doc link to `pci::Device` causes rustdoc warnings:

warning: unresolved link to `kernel::pci::Device`
   --> rust/kernel/device.rs:163:22
    |
163 | /// [`pci::Device`]: kernel::pci::Device
    |                      ^^^^^^^^^^^^^^^^^^^ no item named `pci` in module `kernel`
    |
    = note: `#[warn(rustdoc::broken_intra_doc_links)]` on by default

Fix this by making the documentation conditional on CONFIG_PCI.

Fixes: d6e26c1ae4a6 ("device: rust: expand documentation for Device")
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Reviewed-by: Dirk Behme <dirk.behme@de.bosch.com>
Link: https://patch.msgid.link/20251231045728.1912024-2-fujita.tomonori@gmail.com
[ Keep the "such as" part indicating a list of examples; fix typos in
  commit message. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>