[SYCL][E2E] Fix multiple platform issue in Config/allowlist.cpp test (#20953)

Test was failing on platform having multiple platforms, eg. BMG +
integrated

Author: mateuszpn

sycl/test-e2e/Config/allowlist.cpp

@@ -134,8 +134,17 @@ int main() {
     auto Platforms = sycl::platform::get_platforms();
     if (Platforms.empty())
       throw std::runtime_error("No platform is found");
-    else if (Platforms.size() != 1)
-      throw std::runtime_error("Expected only one platform.");
+
+    std::string FirstName =
+        Platforms.at(0).get_info<sycl::info::platform::name>();
+    std::string FirstVer =
+        Platforms.at(0).get_info<sycl::info::platform::version>();
+    for (const auto &P : Platforms) {
+      if (P.get_info<sycl::info::platform::name>() != FirstName ||
+          P.get_info<sycl::info::platform::version>() != FirstVer) {
+        throw std::runtime_error("Allowlist matched multiple platform types");
+      }
+    }
 
     return 0;
   }