iwlwifi: pcie: Enable MSI mode when using MSI interrupts

On some of the chipsets MSI & INTA interrupts are disabled by default in
the HW registers, and need to be explicitly enabled to be used.

In case MSI-X isn't used, make sure MSI mode is enabled by setting
the relevant HW register.

Signed-off-by: Ido Yariv <idox.yariv@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
diff --git a/drivers/net/wireless/intel/iwlwifi/iwl-prph.h b/drivers/net/wireless/intel/iwlwifi/iwl-prph.h
index 6c1d20d..459bf73 100644
--- a/drivers/net/wireless/intel/iwlwifi/iwl-prph.h
+++ b/drivers/net/wireless/intel/iwlwifi/iwl-prph.h
@@ -417,5 +417,6 @@
 };
 
 #define UREG_CHICK		(0xA05C00)
+#define UREG_CHICK_MSI_ENABLE	BIT(24)
 #define UREG_CHICK_MSIX_ENABLE	BIT(25)
 #endif				/* __iwl_prph_h__ */