[lpc43xx][udc] some basic locking to avoid badness
[lpc43xx][udc] some basic locking to avoid badness

The big bit of unfinished work is supporting multiple queue'd requests
and queueing a request against an endpoint where requests are in progress
(neither work yet, both will result in things getting messed up).

ErikCorryGoogle/lk,srodrig1/lk,ErikCorryGoogle/lk,srodrig1/lk,nvll/lk,minglun-tsai/lk,nvll/lk,travisg/lk,hollanderic/lkstuff,skabet/lk,travisg/lk,GCrean/lk,skabet/lk,minglun-tsai/lk,littlekernel/lk,ErikCorryGoogle/lk,nvll/lk,sndnvaps/lk,minglun-tsai/lk,nvll/lk,GCrean/lk,sndnvaps/lk,srodrig1/lk,hollanderic/lkstuff,minglun-tsai/lk,travisg/lk,sndnvaps/lk,ErikCorryGoogle/lk,travisg/lk,hollanderic/lkstuff,littlekernel/lk,srodrig1/lk,srodrig1/lk,littlekernel/lk,skabet/lk,GCrean/lk,GCrean/lk,skabet/lk,littlekernel/lk,sndnvaps/lk,sndnvaps/lk,hollanderic/lkstuff,GCrean/lk,skabet/lk,nvll/lk