net_sched: remove redundant assignment to ret

The assignment of -EINVAL to variable ret is redundant as it
is being overwritten on the following error exit paths or
to the return value from the following call to basic_set_parms.
Fix this up by removing it. Cleans up clang warning message:

net/sched/cls_basic.c:185:2: warning: Value stored to 'err' is never read

Fixes: 1d8134fe ("net_sched: use idr to allocate basic filter handles")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>