MFC r214160,214162,214236

MFC r214160,214162,214236

r214236 & r214160:
The firmware does pad notifications to an even number of bytes (at least
the association notification), the included information though always
contains an elem block with an odd number of bytes. We handle the last
byte as if it might contain a whole elem block, this of course is not
true as one byte is not enough to hold a block, we therefore discard the
complete frame. The solution here is to subtract one from the actual
notification length, this is also what the Linux driver does. With this
change the frame ends exactly where the last elem block ends.

r214262:
The firmware always sets bit 14 and 15, to get the real associd we need
to clear those bits.

git-svn-id: svn://svn.freebsd.org/base/stable/8@214633 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f