rust: platform: require Send for Driver trait implementers

The instance of Self, returned and created by Driver::probe() is
dropped in the bus' remove() callback.

Request implementers of the Driver trait to implement Send, since the
remove() callback is not guaranteed to run from the same thread as
probe().

Fixes: 683a63b ("rust: platform: add basic platform device / driver abstractions")
Cc: stable <stable@kernel.org>
Reported-by: Alice Ryhl <aliceryhl@google.com>
Closes: https://lore.kernel.org/lkml/Z9rDxOJ2V2bPjj5i@google.com/
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Link: https://lore.kernel.org/r/20250319145350.69543-2-dakr@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Danilo Krummrich

rust/kernel/platform.rs

@@ -149,7 +149,7 @@ macro_rules! module_platform_driver {
 ///     }
 /// }
 ///```
-pub trait Driver {
+pub trait Driver: Send {
     /// The type holding driver private data about each device id supported by the driver.
     ///
     /// TODO: Use associated_type_defaults once stabilized: