um: remove used STDIO_CONSOLE Kconfig param

This removes the STDIO_CONSOLE Kconfig parameter which
is defined but no longer used anywhere in the makefiles and source code.
Signed-off-by: Michael Opdenacker <michael.opdenacker@free-electrons.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/Kconfig.char

@@ -6,10 +6,6 @@ config STDERR_CONSOLE
 	help
 	  console driver which dumps all printk messages to stderr.
 
-config STDIO_CONSOLE
-	bool
-	default y
-
 config SSL
 	bool "Virtual serial line"
 	help