MFC r323128: Increase negotiation polling period from 10ms to 100ms.

There is no big need to burn CPU if other side may be not there yet. For
example, the PLX hardware by default enables the NTB link up on reset, not
dependig on driver to do it. In case of Intel hardware this also reduces
race between MSI-X workaround negotiation and upper layers, using the same
scratchpad registers in different time.