wifi: mac80211: correctly decode TTLM with default link map

In the Linux kernel, the following vulnerability has been resolved:

wifi: mac80211: correctly decode TTLM with default link map

TID-To-Link Mapping (TTLM) elements do not contain any link mapping

presence indicator if a default mapping is used and parsing needs to be

skipped.

Note that access points should not explicitly report an advertised TTLM

with a default mapping as that is the implied mapping if the element is

not included, this is even the case when switching back to the default

mapping. However, mac80211 would incorrectly parse the frame and would

also read one byte beyond the end of the element.