nl80211: Fix handling of if_indices reallocation failure

nl80211: Fix handling of if_indices reallocation failure

Addition of a separate if_indices_reason array broke reallocation
failure checking. drv->if_indices or drv->if_indices_reason could not be
NULL in the place where this check was moved to. Fix that by maintaining
knowledge of reallocation failure in a separate local variable.

Fixes: 732b1d20ec06 ("nl80211: Clean up ifidx properly if interface in a bridge is removed")
Signed-off-by: Jouni Malinen <j@w1.fi>