um: remove unneeded semicolon

while(){}, semicolon do not need to be appended.

Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=2237


Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Richard Weinberger <richard@nod.at>