openrisc: add support for JTAG Serial Port
target: or1k: remove wrong endian swap from or1k generic code

We don't need to swap the endianness in the target generic code.
This swap is necessary because of the adv_debug_if debug unit.
This patch moves this specific piece of code from or1k.c to
or1k_du_adv.c.

Change-Id: I3acea092fe6edfa79b4a87861b5f01204f071bf0
Signed-off-by: Franck Jullien <franck.jullien@gmail.com>