Fix compilation warning in ring library

The following warning is being fixed:

warning: unused imports: `PKCS1`, `PSS`
  --> ring/src/rsa/padding.rs:21:13
   |
21 |     pkcs1::{PKCS1, RSA_PKCS1_SHA256, RSA_PKCS1_SHA384, RSA_PKCS1_SHA512},
   |             ^^^^^
22 |     pss::{PSS, RSA_PSS_SHA256, RSA_PSS_SHA384, RSA_PSS_SHA512},
   |           ^^^
   |
   = note: `#[warn(unused_imports)]` on by default

That warning was already fixed with this patch:
briansmith/ring@c4742e0

Once ring library version will be bumped up, this patch could be dropped.

Signed-off-by: Zbigniew Lukwinski <[email protected]>

external/patches/ring/0001-NFC-Address-Clippy-unused-import-warning.patch

@@ -0,0 +1,29 @@
+From c4742e0cae849f08ff410a817c5266af41670b3d Mon Sep 17 00:00:00 2001
+From: Brian Smith <[email protected]>
+Date: Tue, 9 Jan 2024 10:52:37 -0800
+Subject: [PATCH] NFC: Address Clippy unused import warning.
+
+See https://github.com/briansmith/ring/issues/1887 about addressing this
+messiness long-term.
+---
+ src/rsa/padding.rs | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/src/rsa/padding.rs b/src/rsa/padding.rs
+index faf2422d9..9b79cd0f6 100644
+--- a/src/rsa/padding.rs
++++ b/src/rsa/padding.rs
+@@ -18,8 +18,8 @@ mod pkcs1;
+ mod pss;
+
+ pub use self::{
+-    pkcs1::{PKCS1, RSA_PKCS1_SHA256, RSA_PKCS1_SHA384, RSA_PKCS1_SHA512},
+-    pss::{PSS, RSA_PSS_SHA256, RSA_PSS_SHA384, RSA_PSS_SHA512},
++    pkcs1::{RSA_PKCS1_SHA256, RSA_PKCS1_SHA384, RSA_PKCS1_SHA512},
++    pss::{RSA_PSS_SHA256, RSA_PSS_SHA384, RSA_PSS_SHA512},
+ };
+ pub(super) use pkcs1::RSA_PKCS1_SHA1_FOR_LEGACY_USE_ONLY;
+
+-- 
+2.34.1
+

sh_script/pre-build.sh

@@ -28,6 +28,7 @@ patch-ring() {
             echo "Unsupported target for ring, builds may not work!"
         ;;
     esac
+    git apply ../patches/ring/0001-NFC-Address-Clippy-unused-import-warning.patch
     popd
 }