kill iov_iter_copy_from_user()

all callers can use copy_page_from_iter() and it actually simplifies
them.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --cc fs/ceph/file.c
Simple merge

diff --cc fs/cifs/file.c
Simple merge

diff --cc include/linux/uio.h
Simple merge

diff --cc mm/iov_iter.c
Simple merge

diff --cc mm/process_vm_access.c
Simple merge