tests: Use qpci_mem{read,write} in ivshmem-test

tests: Use qpci_mem{read,write} in ivshmem-test

ivshmem implements a block of shared memory in a PCI BAR.  Currently our
test case accesses this using qtest_mem{read,write}.  However, deducing
the correct addresses for these requires making assumptions about the
internel format returned by qpci_iomap(), along with some ugly casts.

This patch changes the test to use the new qpci_mem{read,write} interfaces
which is neater.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>