dump: const-qualify the buf of WriteCoreDumpFunction

WriteCoreDumpFunction is a function pointer that points to the function used to
write content in "buf" into core file, so "buf" should be const-qualify.

Signed-off-by: Qiao Nuohan <qiaonuohan@cn.fujitsu.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>

dump.c

@@ -99,7 +99,7 @@ static void dump_error(DumpState *s, const char *reason)
     dump_cleanup(s);
 }
 
-static int fd_write_vmcore(void *buf, size_t size, void *opaque)
+static int fd_write_vmcore(const void *buf, size_t size, void *opaque)
 {
     DumpState *s = opaque;
     size_t written_size;

include/qom/cpu.h

@@ -28,7 +28,8 @@
 #include "qemu/tls.h"
 #include "qemu/typedefs.h"
 
-typedef int (*WriteCoreDumpFunction)(void *buf, size_t size, void *opaque);
+typedef int (*WriteCoreDumpFunction)(const void *buf, size_t size,
+                                     void *opaque);
 
 /**
  * vaddr: