Updates to AES countermeasures

-Update comments regarding flag MBEDTLS_AES_SCA_COUNTERMEASURES
-Remove MBEDTLS_AES_SCA_COUNTERMEASURES dependency check
-More comments and coding style changes
diff --git a/include/mbedtls/check_config.h b/include/mbedtls/check_config.h
index 40647d5..fe9c594 100644
--- a/include/mbedtls/check_config.h
+++ b/include/mbedtls/check_config.h
@@ -70,10 +70,6 @@
 #error "MBEDTLS_AESNI_C defined, but not all prerequisites"
 #endif
 
-#if defined(MBEDTLS_AES_SCA_COUNTERMEASURES) && !defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
-#error "MBEDTLS_AES_SCA_COUNTERMEASURES defined, but not all prerequisites"
-#endif
-
 #if defined(MBEDTLS_CTR_DRBG_C) && !defined(MBEDTLS_AES_C)
 #error "MBEDTLS_CTR_DRBG_C defined, but not all prerequisites"
 #endif
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index 1a2de9a..20f1800 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -639,12 +639,12 @@
  *
  * Add countermeasures against possible side-channel-attack to AES calculation.
  *
- * Uncommenting this macro adds three additional calculation rounds to AES
+ * Uncommenting this macro adds additional calculation rounds to AES
  * calculation. Additional rounds are using random data and can occur in any
  * AES calculation round.
  *
- * Tradeoff: Uncommenting this increases ROM footprint by ~800 bytes.
- * The performance loss is 3/11= 27% with 128 bit AES.
+ * Tradeoff: Uncommenting this increases ROM footprint by ~100 bytes.
+ * The performance loss is ~50% with 128 bit AES.
  *
  * This option is dependent of \c MBEDTLS_ENTROPY_HARDWARE_ALT.
  *