brcm80211: Remove bogus memcpy in ai_detach

gcc 4.8 warns for this memcpy. While the copy size is correct, the whole
copy seems to be a nop because the destination is never used, and
there's no need to use memcpy to copy pointers anyways. And the
type of the pointer was wrong, but at least those are always the same.

Just remove it.

/backup/lsrc/git/linux-lto-2.6/drivers/net/wireless/brcm80211/brcmsmac/aiutils.c: In function 'ai_detach':
/backup/lsrc/git/linux-lto-2.6/drivers/net/wireless/brcm80211/brcmsmac/aiutils.c:539:32: warning: argument to 'sizeof' in 'memcpy' call is the same pointer type 'struct si_pub **' as the destination; expected 'struct si_pub *' or an explicit length [-Wsizeof-pointer-memaccess]
  memcpy(&si_local, &sih, sizeof(struct si_pub **));
                                ^

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>