char: mware: fix returnvar.cocci warnings

Remove unneeded variables when "0" can be returned.

Generated by: scripts/coccinelle/misc/returnvar.cocci

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: jing yangyang <jing.yangyang@zte.com.cn>
Link: https://lore.kernel.org/r/20210820021752.10927-1-jing.yangyang@zte.com.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>