chardev: Properly initialize ChardevCommon components

Commit d0d7708b forgot to parse logging for spice chardevs and
virtual consoles. This requires making qemu_chr_parse_common()
non-static. While at it, use a temporary variable to make the
code shorter, as well as reduce the churn when a later patch
alters the layout of simple unions.

Signed-off-by: Eric Blake <eblake@redhat.com>
CC: Daniel P. Berrange <berrange@redhat.com>
Message-Id: <1455927587-28033-2-git-send-email-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/sysemu/char.h

@@ -114,6 +114,16 @@ CharDriverState *qemu_chr_new_from_opts(QemuOpts *opts,
                                     void (*init)(struct CharDriverState *s),
                                     Error **errp);
 
+/**
+ * @qemu_chr_parse_common:
+ *
+ * Parse the common options available to all character backends.
+ *
+ * @opts the options that still need parsing
+ * @backend a new backend
+ */
+void qemu_chr_parse_common(QemuOpts *opts, ChardevCommon *backend);
+
 /**
  * @qemu_chr_new:
  *