This is the companion to PR #766. It removes the CONFIG_CAN_PASS_STRUCT option as recommended by Issue #620
NuttX PR #766 depends on PR being in place but not vice versa. This PR should be merge-able without #766 and then PR #766 should also pass its checks.
1.Remove void cast for function because many place ignore the returned value witout cast
2.Replace void cast for variable with UNUSED macro
Change-Id: Ie644129a563244a6397036789c4c3ea83c4e9b09
Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
