FROMLIST: brcmfmac: fix initialization of struct cfg80211_inform_bss variable

This patch fixes a sparse warning "Using plain integer as NULL pointer"
about cfg80211_inform_bss structure initialization.

Reported-by: kbuild test robot <lkp@intel.com>
Reviewed-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Franky Lin <franky.lin@broadcom.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
(cherry picked from commit 763ece85f45a6b93268e25a0abf02922f911dab4)

Change-Id: If5a64df0fcaeb56435678a142b71a33e4f3e45b2