net/mlx5: Shift control IRQ to the last index

Control IRQ is the first IRQ vector. This complicates handling of
completion irqs as we need to offset them by one.
in the next patch, there are scenarios where completion and control EQs
will share the same irq. for example: functions with single IRQ. To ease
such scenarios, we shift control IRQ to the end of the irq array.

Signed-off-by: Shay Drory <shayd@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>