kernel/groups.c: remove return value of set_groups

kernel/groups.c: remove return value of set_groups

After commit 6307f8fee295 ("security: remove dead hook task_setgroups"),
set_groups will always return zero, so we could just remove return value
of set_groups.

This patch reduces code size, and simplfies code to use set_groups,
because we don't need to check its return value any more.

[[email protected]: remove obsolete claims from set_groups() comment]
Signed-off-by: Wang YanQing <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Cc: Serge Hallyn <[email protected]>
Cc: Eric Paris <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>