staging: brcm80211: modify the FOREACH_BSS macro

The FOREACH_BSS macro was changed to remove a checkpatch error. However,
the patch was considered ugly. This patch is another attempt to make it
more clear. END_FOREACH_BSS is defined with braces to avoid an invalid
checkpatch.pl warning. Ideally, the checkpatch.pl script should be adapted
but lacking good perl knowledge to do so.

Reported-by: Dan Carpenter <error27@gmail.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Roland Vossen <rvossen@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>