iwlwifi: eeprom-parse: use struct_size() in kzalloc()

One of the more common cases of allocation size calculations is finding the
size of a structure that has a zero-sized array at the end, along with memory
for some number of elements for that array. For example:

struct foo {
    int stuff;
    void *entry[];
};

instance = kzalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL);

Instead of leaving these open-coded and prone to type mistakes, we can now
use the new struct_size() helper:

instance = kzalloc(struct_size(instance, entry, count), GFP_KERNEL);

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

drivers/net/wireless/intel/iwlwifi/iwl-eeprom-parse.c

@@ -850,8 +850,7 @@ iwl_parse_eeprom_data(struct device *dev, const struct iwl_cfg *cfg,
 	if (WARN_ON(!cfg || !cfg->eeprom_params))
 		return NULL;
 
-	data = kzalloc(sizeof(*data) +
-		       sizeof(struct ieee80211_channel) * IWL_NUM_CHANNELS,
+	data = kzalloc(struct_size(data, channels, IWL_NUM_CHANNELS),
 		       GFP_KERNEL);
 	if (!data)
 		return NULL;