wifi: brcmfmac: remove redundant variable err

Return value from brcmf_fil_iovar_data_set() and
brcmf_config_ap_mgmt_ie() directly instead of
taking this in another redundant variable.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Jinpeng Cui <cui.jinpeng2@zte.com.cn>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220831132254.303697-1-cui.jinpeng2@zte.com.cn