mlx4: limit max MSIX allocations

mlx4: limit max MSIX allocations

We get more than 64 MSI-X vectors from CX3 firmware 2.35.5530 onwards.
This results in in legacy mode EQ allocs after 64 EQs, which ends up
flooding 3 vectors and causing performance degradation.

With this patch, we limit max vector allocations MAX_MSIX(64).
When Mellanox driver can support more EQs without getting into legacy
mode, this patch should go away.

Orabug: 25912737

Signed-off-by: Ajaykumar Hotchandani <ajaykumar.hotchandani@oracle.com>
Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>