staging: brcm80211: revert removal of atomic initialization

The commit "staging: brcm80211: remove code for unsupported chip"
unintentionally got rid of initialization of the atomic variable
brcmf_mmc_suspend. The patch restore that particular piece of code.

Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>