ntb_hw_amd: Fix incorrect debug message in link disable path

amd_ntb_link_disable() prints "Enabling Link" which is misleading.
Update the message to reflect that the link is being disabled.

Signed-off-by: Alok Tiwari <alok.a.tiwari@oracle.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>