tty: vt, too many commands per line in rgb_foreground

Do not opencode max3, use the macro.

Separate commands. Until now, I have not noticed the comma. Make it
one line, one command. And make the code obvious.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>