As there's potential for failure of the nla_memdup(),
check the return value.

Fixes: a442b761 ("cfg80211: add add_nan_func / del_nan_func")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Link: https://lore.kernel.org/r/20220301100020.3801187-1-jiasheng@iscas.ac.cnSigned-off-by: Johannes Berg <johannes.berg@intel.com>