NTB: set peer_sta within event handler itself

amd_ack_smu() should only set the corresponding
bits into SMUACK register. Setting the bitmask
of peer_sta should be done within the event handler.
They are two different things, and so should be
handled differently and at different places.

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