tcg: Move TCG_TYPE_COUNT outside enum

The count is not itself an enumerator.  Move it outside to
prevent the compiler from considering it with -Wswitch-enum.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

include/tcg/tcg.h

@@ -294,7 +294,8 @@ typedef enum TCGType {
     TCG_TYPE_V128,
     TCG_TYPE_V256,
 
-    TCG_TYPE_COUNT, /* number of different types */
+    /* Number of different types (integer not enum) */
+#define TCG_TYPE_COUNT  (TCG_TYPE_V256 + 1)
 
     /* An alias for the size of the host register.  */
 #if TCG_TARGET_REG_BITS == 32