saned: update man for option -b

doc/saned.man

@@ -6,6 +6,9 @@ saned \- SANE network daemon
 .B saned
 .B [ \-a
 .I [ username ]
+.B [ \-b
+.I address
+.B ]
 .B | \-d
 .I [ n ]
 .B | \-s
@@ -59,6 +62,12 @@ is used, the debug messages will be printed to stderr while
 .B \-s
 requests using syslog.
 .PP
+The
+.B \-b
+flag requests that
+.B saned
+bind to a specific address.
+.PP
 If
 .B saned
 is run from inetd, xinetd or systemd, no option can be given.