fs/locks: Remove redundant assignment to cmd

Variable 'cmd' set but not used.

fs/locks.c:2428:3: warning: Value stored to 'cmd' is never read.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=4439
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>