In breaking patch buf memory moved from stack to heap and sizeof(buf)
change from size of actual memory to size of the pointer to the heap.

Fix this by holding a separated variable for allocate size.

Fixes: 01f84f0e ("mac80211: reduce stack usage in debugfs")
Signed-off-by: Mordechay Goodstein <mordechay.goodstein@intel.com>
Link: https://lore.kernel.org/r/20211021163035.b9ae48c06e27.I6a6ed197110eae28cf4f6e38ce36828a7c136337@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>