rust: pci: fix incorrect platform reference in PCI driver probe doc comment

Substitute 'platform' with 'pci'.

Fixes: 1bd8b6b2 ("rust: pci: add basic PCI device / driver abstractions")
Cc: stable@kernel.org
Signed-off-by: Rahul Rameshbabu <sergeantsagara@protonmail.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>