chardev: Properly initialize ChardevCommon components

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 <[email protected]>
CC: Daniel P. Berrange <[email protected]>
Message-Id: <1455927587[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>