MSI/powerpc: Use __read_msi_msg() instead of read_msi_msg()
rtas_setup_msi_irqs() already has the struct msi_desc pointer required by
__read_msi_msg(), so call it directly instead of having read_msi_msg() look
it up from the IRQ.
No functional change.
[bhelgaas: changelog] Signed-off-by: Yijing Wang <wangyijing@huawei.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Acked-by: Michael Ellerman <mpe@ellerman.id.au> CC: Benjamin Herrenschmidt <benh@kernel.crashing.org> CC: linuxppc-dev@lists.ozlabs.org