Make it a style to reduce code duplication

OpenKeychain/src/main/res/values/styles.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<resources>
+<resources xmlns:tools="http://schemas.android.com/tools">
 
     <style name="CardViewHeader">
         <item name="android:drawableBottom">?attr/cardViewHeaderDrawable</item>
@@ -38,4 +38,9 @@
         <item name="android:textColor">?attr/colorAccent</item>
     </style>
 
+    <!-- constrain size of backup code input for smaller devices -->
+    <style name="BackupCodeTextStyle">
+        <item name="android:textSize" tools:ignore="SpUsage">14dp</item>
+    </style>
+
 </resources>