NTB: move ntb_ctrl handling to init and deinit

It does not really make sense to enable or disable
the bits of NTB_CTRL register only during enable
and disable link callbacks. They should be done
independent of these callbacks. The correct placement
for that is during the amd_init_side_info() and
amd_deinit_side_info() functions, which are invoked
during probe and remove respectively.

Signed-off-by: Arindam Nath <arindam.nath@amd.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>