CONFIG_CON_CHAN is not available for thedefaultarchitecture x86.
Result is shown for architecture um

Default console channel initialization

configname: CONFIG_CON_CHAN

Linux Kernel Configuration
└─>UML Character Devices
└─>Default console channel initialization
In linux kernel since version 2.6.12  
This is the string describing the channel to which all consoles
except the main console will be attached by default. This value can
be overridden from the command line. The default value is "xterm",
which brings them up in xterms.
It is safe to leave this unchanged, although you may wish to change
this if you expect the UML that you build to be run in environments
which don't have X or xterm available.