serdev: enable TTY port controller support by default

Amend the Serial device bus Kconfig entries to clarify that you most
likely also want to enable TTY port controller support, and make
SERIAL_DEV_CTRL_TTYPORT default to Y (when bus support is enabled).

Note that the TTY port controller is currently the only in-kernel
serdev controller implementation.

Signed-off-by: Johan Hovold <[e-mail]>
Reviewed-by: Sebastian Reichel <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/tty/serdev/Kconfig

···
 	help
 	  Core support for devices connected via a serial port.
 
+	  Note that you typically also want to enable TTY port controller support.
+
 if SERIAL_DEV_BUS
 
 config SERIAL_DEV_CTRL_TTYPORT
 	bool "Serial device TTY port controller"
+	help
+	  Say Y here if you want to use the Serial device bus with common TTY
+	  drivers (e.g. serial drivers).
+
+	  If unsure, say Y.
 	depends on TTY
 	depends on SERIAL_DEV_BUS != m
+	default y
 
 endif