MN10300: Remove monitor/JTAG functions

Remove the monitor trap function and the set_jtag_stub function as they're not
really necessary.

Signed-off-by: Akira Takeuchi <takeuchi.akr@jp.panasonic.com>
Signed-off-by: Kiyoshi Owada <owada.kiyoshi@jp.panasonic.com>
Signed-off-by: David Howells <dhowells@redhat.com>