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

Substitute 'platform' with 'pci'.

Fixes: 18ebb25 ("rust: pci: implement Driver::unbind()")
Cc: stable@kernel.org
Signed-off-by: Rahul Rameshbabu <sergeantsagara@protonmail.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Author: Binary-Eater

rust/kernel/pci.rs

@@ -274,7 +274,7 @@ pub trait Driver: Send {
     /// Implementers should attempt to initialize the device here.
     fn probe(dev: &Device<device::Core>, id_info: &Self::IdInfo) -> Result<Pin<KBox<Self>>>;
 
-    /// Platform driver unbind.
+    /// PCI driver unbind.
     ///
     /// Called when a [`Device`] is unbound from its bound [`Driver`]. Implementing this callback
     /// is optional.