mac80211: remove pointless mesh path timer RCU code

The code here to RCU-dereference a pointer that's
on the stack is totally pointless, RCU isn't magic
(like say Java's weak references are), so the code
can't work like whoever wrote it thought it might.

Remove it so readers don't get confused. Note that
it seems that a bug is there anyway: I don't see
any code that cancels the timer when a mesh path
struct is destroyed.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>