or1k: initialization of the jtag tap moved to distinct file

Created new file (or1k_tap.c) that holds or1k_jtag_init
function. This function handles initialisation of both
vjtag and opencores jtag (accordingly to configure options).

Signed-off-by: Marek Czerski <ma.czerski@gmail.com>
Signed-off-by: Franck Jullien <franck.jullien@gmail.com>
or1k: remove some jtag init globals

Remove globals or1k_jtag_inited and or1k_jtag_module_selected and
make those variable part of struct or1k_jtag.

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