brcmfmac: fix clearing entry IPv6 address

brcmfmac: fix clearing entry IPv6 address

When IPv6 address is to be cleared there is a possible out of
bound access. But also the clearing of the last entry and the
adjustment of total number of stored IPv6 addresses is not
updated. This patch fixes that bug. Bug was found using coverity.

Reviewed-by: Arend Van Spriel <arend.vanspriel@broadcom.com>
Reviewed-by: Franky Lin <franky.lin@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieter-paul.giesberts@broadcom.com>
Signed-off-by: Hante Meuleman <hante.meuleman@broadcom.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>