NTB: return the side info status from amd_poll_link

Bit 1 of SIDE_INFO register is an indication that
the driver on the other side of link is ready. We
set this bit during driver initialization sequence.
So rather than having separate macros to return the
status, we can simply return the status of this bit
from amd_poll_link(). So a return of 1 or 0 from
this function will indicate to the caller whether
the driver on the other side of link is ready or not,
respectively.

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