cifs: remove unused parameter from cifs_posix_open_inode_helper()

..a left over from the commit 3321b791

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Cc: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Steve French <sfrench@us.ibm.com>