Revert "9p: init_in_iov_from_pdu can truncate the size"

Revert "9p: init_in_iov_from_pdu can truncate the size"

This reverts commit 16724a173049ac29c7b5ade741da93a0f46edff7.
It causes https://bugs.launchpad.net/bugs/1877688.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
Reviewed-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Message-Id: <20200521192627.15259-1-sstabellini@kernel.org>
Signed-off-by: Greg Kurz <groug@kaod.org>
(cherry picked from commit cf45183b718f02b1369e18c795dc51bc1821245d)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>