smb: client: Remove redundant check in cifs_oplock_break()

There is an unnecessary NULL check of inode in cifs_oplock_break(), since
there are multiple dereferences of cinode prior to it.

Based on usage of cifs_oplock_break() in cifs_new_fileinfo() we can safely
assume that inode is not NULL, so there is no need to check inode in
cifs_oplock_break() at all.

Therefore, this redundant check can be removed.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Signed-off-by: Ivan Abramov <i.abramov@mt-integration.ru>
Signed-off-by: Steve French <stfrench@microsoft.com>