mac80211: fix ht_capa printout in debugfs

Don't use sizeof(pointer) when calculating scnprintf offset.

Fixes: 01f84f0ed3 ("mac80211: reduce stack usage in debugfs")
Signed-off-by: Ben Greear <greearb@candelatech.com>
Link: https://lore.kernel.org/r/20220406175659.20611-1-greearb@candelatech.com
[correct the Fixes tag]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/debugfs_sta.c

@@ -441,7 +441,7 @@ static ssize_t sta_ht_capa_read(struct file *file, char __user *userbuf,
 #define PRINT_HT_CAP(_cond, _str) \
 	do { \
 	if (_cond) \
-			p += scnprintf(p, sizeof(buf)+buf-p, "\t" _str "\n"); \
+			p += scnprintf(p, bufsz + buf - p, "\t" _str "\n"); \
 	} while (0)
 	char *buf, *p;
 	int i;