lustre: Deletion of unnecessary checks before three function calls

The functions free_ll_remote_perm(), free_rmtperm_hash() and iput() test
whether their argument is NULL and then return immediately.
Thus the test around their calls is not needed.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>