NTB: ntb_perf: Increased the number of message retries to 1000

while waiting for the peer ntb_perf to initialize scratchpad
registers, local side ntb_perf  might have already exhausted the
maximum number of retries which is currently set to 500. To avoid
this and to give little more time to the peer ntb_perf for scratchpad
initialization, increased the number of retries to 1000

Signed-off-by: Sanjay R Mehta <sanju.mehta@amd.com>
Acked-by: Allen Hubbe <allenbh@gmail.com>
Acked-by: Logan Gunthorpe <logang@deltatee.com>
Acked-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>