tty: source all tty Kconfig files in one place

'source' (include) all of the tty/*/Kconfig files from
drivers/tty/Kconfig instead of from drivers/char/Kconfig.
This consolidates them both in source code and in menu
presentation to the user.

Move hvc/Kconfig and serial/Kconfig 'source' lines into the
if TTY/endif block and remove the if TTY/endif blocks from
those 2 files.

Cc: linux-serial@vger.kernel.org
Cc: Jiri Slaby <jslaby@suse.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Suggested-by: Jiri Slaby <jslaby@suse.com>
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20200311225736.32147-3-rdunlap@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/hvc/Kconfig

@@ -1,5 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0
-if TTY
 
 config HVC_DRIVER
 	bool
@@ -113,5 +112,3 @@ config HVCS
 	  will depend on arch specific APIs exported from hvcserver.ko
 	  which will also be compiled when this driver is built as a
 	  module.
-
-endif # TTY