iwlwifi: remove unneeded NULL check

There's no need to check trans for non-null
here as it has already been checked in the
caller. This fixes an smatch warning that we
check after having dereferenced it.
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/iwlwifi/pcie/rx.c

@@ -879,9 +879,6 @@ static irqreturn_t iwl_isr(int irq, void *data)
 
 	lockdep_assert_held(&trans_pcie->irq_lock);
 
-	if (!trans)
-		return IRQ_NONE;
-
 	trace_iwlwifi_dev_irq(trans->dev);
 
 	/* Disable (but don't clear!) interrupts here to avoid