Bug 1606119 - Fix PPC HW Crypto build failure r=jcj

All Altivec *_be() functions are supported from gcc version 8.x not 5.x
so modify gcc version check that at the moment cause build failure due
to missing Altivec *_be() functions.

--HG--
extra : amend_source : 217aa37aba9f07e4fd72e8dfd7a9fa49b31fca93

lib/freebl/gcm.h

@@ -41,11 +41,11 @@
 #endif
 
 /*
- * PPC CRYPTO requires at least gcc 5 or clang. The LE check is purely
+ * PPC CRYPTO requires at least gcc 8 or clang. The LE check is purely
  * because it's only been tested on LE. If you're interested in BE,
  * please send a patch.
  */
-#if (defined(__clang__) || (defined(__GNUC__) && __GNUC__ >= 5)) && \
+#if (defined(__clang__) || (defined(__GNUC__) && __GNUC__ >= 8)) && \
     defined(IS_LITTLE_ENDIAN)
 #define USE_PPC_CRYPTO
 #endif