[CIFS] Remove redundant test

In fs/cifs/cifssmb.c, pLockData is tested for being NULL at the beginning
of the function, and not reassigned subsequently.

A simplified version of the semantic patch that makes this change is as
follows: (http://www.emn.fr/x-info/coccinelle/)

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Steve French <sfrench@us.ibm.com>