Allow variant summary of enhanced 4G LTE mode

Carrier persist to change the summary of enhanced 4G LTE mode, like O2.
Reuse KEY_ENHANCED_4G_LTE_TITLE_VARIANT_INT to customize the summary.

Bug: 119289864
Test: Manual test
Change-Id: I8050349c79df23f14074653ba36c5016bf306ad8
diff --git a/res/values/strings.xml b/res/values/strings.xml
index d6c5fd7..b3889dd 100644
--- a/res/values/strings.xml
+++ b/res/values/strings.xml
@@ -530,6 +530,16 @@
 
     <!-- Mobile network 4G summary [CHAR LIMIT=80] -->
     <string name="enhanced_4g_lte_mode_summary">Use LTE services to improve voice and other communications (recommended)</string>
+    <string name="enhanced_4g_lte_mode_summary_o2">Use 4G services to improve voice and other communications (recommended)</string>
+    <!-- Carrier variant of Enhaced 4G LTE Mode summary.  [CHAR LIMIT=80] -->
+    <string-array name="enhanced_4g_lte_mode_sumary_variant">
+        <!-- 0: Default -->
+        <item>@string/enhanced_4g_lte_mode_summary</item>
+        <!-- 1: Verizon -->
+        <item>@string/enhanced_4g_lte_mode_summary</item>
+        <!-- 2: O2 UK -->
+        <item>@string/enhanced_4g_lte_mode_summary_o2</item>
+    </string-array>
 
     <!-- Mobile network settings screen, data enabling checkbox name -->
     <string name="data_enabled">Data enabled</string>