switch elf_core_write_extra_data() to dump_emit()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 35c4886..a998b22 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -2196,8 +2196,10 @@
 		}
 	}
 
-	if (!elf_core_write_extra_data(cprm->file, &size, cprm->limit))
+	cprm->written = size;
+	if (!elf_core_write_extra_data(cprm))
 		goto end_coredump;
+	size = cprm->written;
 
 	if (e_phnum == PN_XNUM) {
 		size += sizeof(*shdr4extnum);