tcg-arm: fix a typo in comments

ARM still doesn't support 16GB buffers in 32-bit modes, replace the
16GB by 16MB in the comment.
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NAurelien Jarno <aurelien@aurel32.net>
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>

exec.c

@@ -511,7 +511,7 @@ static void code_gen_alloc(unsigned long tb_size)
         if (code_gen_buffer_size > (512 * 1024 * 1024))
             code_gen_buffer_size = (512 * 1024 * 1024);
 #elif defined(__arm__)
-        /* Keep the buffer no bigger than 16GB to branch between blocks */
+        /* Keep the buffer no bigger than 16MB to branch between blocks */
         if (code_gen_buffer_size > 16 * 1024 * 1024)
             code_gen_buffer_size = 16 * 1024 * 1024;
 #elif defined(__s390x__)

tcg/arm/tcg-target.c

@@ -843,7 +843,7 @@ static inline void tcg_out_st8(TCGContext *s, int cond,
 }
 
 /* The _goto case is normally between TBs within the same code buffer,
- * and with the code buffer limited to 16GB we shouldn't need the long
+ * and with the code buffer limited to 16MB we shouldn't need the long
  * case.
  *
  * .... except to the prologue that is in its own buffer.