staging: brcm80211: remove unused dhd_ops_virt variable definition

The variable dhd_ops_virt was used before although its use was rather
limited as can be found in previous commit:

| commit 4fd68ae1
| Author: Julia Lawall <julia@diku.dk>
| Date:   Tue Oct 26 12:25:33 2010 +0200
|
|    drivers/staging/brcm80211/brcmfmac/dhd_linux.c: delete double assignment
|

Reviewed-by: Roland Vossen <rvossen@broadcom.com>
Reviewed-by: Brett Rudley <brudley@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>