flatload: fix bss clearing

The current bss clear logic assumes the target mmap address and host
address are the same.  Use g2h to translate from the target address
space to the host so we can call memset on it.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

linux-user/flatload.c

@@ -660,7 +660,7 @@ static int load_flat_file(struct linux_binprm * bprm,
     }
 
     /* zero the BSS.  */
-    memset((void *)((unsigned long)datapos + data_len), 0, bss_len);
+    memset(g2h(datapos + data_len), 0, bss_len);
 
     return 0;
 }