net/mlx5: Fix error print in case of IRQ request failed

In case IRQ layer failed to find or to request irq, the driver is
printing the first cpu of the provided affinity as part of the error
print. Empty affinity is a valid input for the IRQ layer, and it is
an error to call cpumask_first() on empty affinity.

Remove the first cpu print from the error message.

Fixes: c36326d3

 ("net/mlx5: Round-Robin EQs over IRQs")
Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Moshe Shemesh <moshe@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>