net: sched: Fix spelling mistakes

Fix some spelling mistakes in comments:
sevaral  ==> several
sugestion  ==> suggestion
unregster  ==> unregister
suplied  ==> supplied
cirsumstances  ==> circumstances

Signed-off-by: Zheng Yongjun <zhengyongjun3@huawei.com>
Link: https://lore.kernel.org/r/20210531020048.2920054-1-zhengyongjun3@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>