iov_iter: fix ubuf iter

Hello

JIRA: https://issues.redhat.com/browse/RHEL-87739

So far, we just run one partial backport on the following upstream PR to rhel9, and cause bug in code which depends on ITER_UBUF.

https://lore.kernel.org/all/f16053ea-d3b8-a8a2-0178-3981fea5a656@kernel.dk/

This MR pulls the other 4 missed patches to rhel9.

Signed-off-by: Ming Lei ming.lei@redhat.com