smb: client: Remove redundant check in smb2_is_path_accessible()

There is an unnecessary NULL check of cifs_sb in smb2_is_path_accessible(),
since cifs_sb is dereferenced multiple times prior to it.

It seems that there is no need to introduce any NULL checks of cifs_sb,
since arguments of smb2_is_path_accessible() are assumed to be non-NULL.

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>