Rename and document new configuration option for packing AES tables

This commit renames the new AES table packing option introduced in the
previous MBEDTLS_AES_PACK_TABLES and documents its use and memory vs.
speed tradeoff. It also enhances the documentation of the other
AES-related option MBEDTLS_AES_ROM_TABLES.

library/version_features.c

diff --git a/library/version_features.c b/library/version_features.c
index 2b65199..549f40d 100644
--- a/library/version_features.c
+++ b/library/version_features.c
@@ -198,9 +198,9 @@
 #if defined(MBEDTLS_AES_ROM_TABLES)
     "MBEDTLS_AES_ROM_TABLES",
 #endif /* MBEDTLS_AES_ROM_TABLES */
-#if defined(MBEDTLS_AES_SMALL_TABLES)
-    "MBEDTLS_AES_SMALL_TABLES",
-#endif /* MBEDTLS_AES_SMALL_TABLES */
+#if defined(MBEDTLS_AES_FEWER_TABLES)
+    "MBEDTLS_AES_FEWER_TABLES",
+#endif /* MBEDTLS_AES_FEWER_TABLES */
 #if defined(MBEDTLS_CAMELLIA_SMALL_MEMORY)
     "MBEDTLS_CAMELLIA_SMALL_MEMORY",
 #endif /* MBEDTLS_CAMELLIA_SMALL_MEMORY */