rust: kernel: fix THIS_MODULE header path in ThisModule doc comment

The doc comment for `ThisModule` incorrectly states the C header file
for `THIS_MODULE` as `include/linux/export.h`, while the correct path is
`include/linux/init.h`. This is because `THIS_MODULE` was moved in
commit 5b20755 ("init: move THIS_MODULE from <linux/export.h> to
<linux/init.h>").

Update the doc comment for `ThisModule` to reflect the correct header
file path for `THIS_MODULE`.

Fixes: 5b20755 ("init: move THIS_MODULE from <linux/export.h> to <linux/init.h>")
Signed-off-by: Yutaro Ohno <[email protected]>
Reviewed-by: Greg Kroah-Hartman <[email protected]>
Link: https://lore.kernel.org/r/ZxXDZwxWgoEiIYkj@ohnotp
Signed-off-by: Miguel Ojeda <[email protected]>

Author: ohno418

rust/kernel/lib.rs

@@ -85,7 +85,7 @@ pub trait Module: Sized + Sync + Send {
 
 /// Equivalent to `THIS_MODULE` in the C API.
 ///
-/// C header: [`include/linux/export.h`](srctree/include/linux/export.h)
+/// C header: [`include/linux/init.h`](srctree/include/linux/init.h)
 pub struct ThisModule(*mut bindings::module);
 
 // SAFETY: `THIS_MODULE` may be used from all threads within a module.