match_string() returns the index of an array for a matching string,
which can be used intead of open coded variant.
Signed-off-by: NYisheng Xie <xieyisheng1@huawei.com>
Reviewed-by: NTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>