CodingStyle: Fix documentation on use of C99 types.

Reality has it that new code is discouraged from using C99 exact width
types.  Fix the documentation.

Signed-off-by: Mike Waychison <mikew@google.com>
diff --git a/Documentation/CodingStyle b/Documentation/CodingStyle
index 8bb3723..8dd2e77 100644
--- a/Documentation/CodingStyle
+++ b/Documentation/CodingStyle
@@ -323,8 +323,7 @@ useful only for:
 
      Therefore, the Linux-specific 'u8/u16/u32/u64' types and their
      signed equivalents which are identical to standard types are
-     permitted -- although they are not mandatory in new code of your
-     own.
+     preferred.
 
      When editing existing code which already uses one or the other set
      of types, you should conform to the existing choices in that code.