rust: firmware: fix invalid rustdoc link

remove an extra quote from the doc comment so that rustdoc
no longer genertes a link to a nonexistent file.

Signed-off-by: Andrew Ballance <andrewjballance@gmail.com>
Reviewed-by: Danilo Krummrich <dakr@redhat.com>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Fixes: de65828 ("rust: add firmware abstractions")
Link: https://lore.kernel.org/r/20240709004426.44854-1-andrewjballance@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: mrwigglewaffles

rust/kernel/firmware.rs

@@ -2,7 +2,7 @@
 
 //! Firmware abstraction
 //!
-//! C header: [`include/linux/firmware.h`](srctree/include/linux/firmware.h")
+//! C header: [`include/linux/firmware.h`](srctree/include/linux/firmware.h)
 
 use crate::{bindings, device::Device, error::Error, error::Result, str::CStr};
 use core::ptr::NonNull;