accel/habanalabs: remove unneeded irq_handler variable

'irq_handler' in gaudi2_enable_msix(), is just assigned with a function
name and then used when calling request_threaded_irq().
Remove the variable and use the function name directly as an argument.

Signed-off-by: Tomer Tayar <ttayar@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>
Reviewed-by: Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com>