efi: Deduplicate configuration table search function

We do table search in many places doing exactly the same algorithm.
The only minor variance in users is which table is used if several entries
are present. As specification mandates uniqueness and even if it ever isn't,
first entry is good enough, unify this code and always use the first entry.

Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

grub-core/kern/efi/efi.c

@@ -1031,3 +1031,21 @@ grub_efi_compare_device_paths (const grub_efi_device_path_t *dp1,
 
   return 0;
 }
+
+void *
+grub_efi_find_configuration_table (const grub_guid_t *target_guid)
+{
+  unsigned i;
+
+  for (i = 0; i < grub_efi_system_table->num_table_entries; i++)
+    {
+      grub_guid_t *guid =
+	&grub_efi_system_table->configuration_table[i].vendor_guid;
+
+      if (! grub_memcmp (guid, target_guid, sizeof (grub_guid_t)))
+	return (void *)
+	  grub_efi_system_table->configuration_table[i].vendor_table;
+    }
+
+  return 0;
+}