cifs: remove unneeded condition check

file->private_data can never be null after calling initiate_cifs_search.
So private null check condition is not needed.

Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Ashish Sangwan <a.sangwan@samsung.com>
Signed-off-by: Steve French <steve.french@primarydata.com>