iwlwifi: pcie: make sure prph_info is set when treating wakeup IRQ

In some rare cases when the HW is in a bad state, we may get this
interrupt when prph_info is not set yet.  Then we will try to
dereference it to check the sleep_notif element, which will cause an
oops.

Fix that by ignoring the interrupt if prph_info is not set yet.
Signed-off-by: NLuca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20211219132536.0537aa562313.I183bb336345b9b3da196ba9e596a6f189fbcbd09@changeidSigned-off-by: NLuca Coelho <luciano.coelho@intel.com>

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

@@ -2266,7 +2266,12 @@ irqreturn_t iwl_pcie_irq_msix_handler(int irq, void *dev_id)
 		}
 	}
 
-	if (inta_hw & MSIX_HW_INT_CAUSES_REG_WAKEUP) {
+	/*
+	 * In some rare cases when the HW is in a bad state, we may
+	 * get this interrupt too early, when prph_info is still NULL.
+	 * So make sure that it's not NULL to prevent crashing.
+	 */
+	if (inta_hw & MSIX_HW_INT_CAUSES_REG_WAKEUP && trans_pcie->prph_info) {
 		u32 sleep_notif =
 			le32_to_cpu(trans_pcie->prph_info->sleep_notif);
 		if (sleep_notif == IWL_D3_SLEEP_STATUS_SUSPEND ||