Add deprecated attribute to depracted functions

bindgen does add the deprecated attribute to deprecated functions.  This patch
manually adds the attributes libnitrokey’s deprecated functions.
Index: nitrokey-sys-rs/src/ffi.rs
===================================================================
--- nitrokey-sys-rs.orig/src/ffi.rs
+++ nitrokey-sys-rs/src/ffi.rs
@@ -762,6 +762,7 @@ extern "C" {
     #[doc = " deprecated in favor of NK_get_status_as_string."]
     #[doc = " @return string representation of the status or an empty string"]
     #[doc = "         if the command failed"]
+    #[deprecated(since = "3.5.0", note="use `NK_get_status_as_string` instead")]
     pub fn NK_status() -> *mut ::std::os::raw::c_char;
 }
 extern "C" {
@@ -1017,6 +1018,7 @@ extern "C" {
     pub fn NK_totp_set_time_soft(time: u64) -> ::std::os::raw::c_int;
 }
 extern "C" {
+    #[deprecated(since = "3.4.0", note="use `NK_totp_set_time_soft` instead")]
     pub fn NK_totp_get_time() -> ::std::os::raw::c_int;
 }
 extern "C" {