ubi: block: Remove in vain semicolon

Remove the repeated ';' from code, it is not
needed.

Signed-off-by: Li zeming <zeming@nfschina.com>
Reviewed-by: Zhihao Cheng <chengzhihao1@huawei.com>
[rw: Massaged commit message a bit]
Signed-off-by: Richard Weinberger <richard@nod.at>