tty: remove bfin_jtag_comm and hvc_bfin_jtag drivers

The blackfin architecture is getting removed, so these drivers
are not needed any more.

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Aaron Wu <aaron.wu@analog.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>