IB/ipoib: Scatter-Gather support in connected mode

IB/ipoib: Scatter-Gather support in connected mode

By default, IPoIB-CM driver uses 64k MTU. Larger MTU gives better performance.
This MTU plus overhead puts the memory allocation for IP based packets at 32
4k pages (order 5), which have to be contiguous.
When the system memory under pressure, it was observed that allocating 128k
contiguous physical memory is difficult and causes serious errors (such as
system becomes unusable).
This enhancement resolve the issue by removing the physically contiguous memory
requirement using Scatter/Gather feature that exists in Linux stack.

With this fix Scatter-Gather will be supported also in connected mode
This change also revert the change made in commit e112373
("IPoIB/cm: Reduce connected mode TX object size)".

Orabug: 20422840

Reviewed-by: John Sobecki <john.sobecki@oracle.com>
Signed-off-by: Yuval Shaia <yuval.shaia@oracle.com>