PCI/MSI: Use __get_cached_msi_msg() instead of get_cached_msi_msg()

Both callers of get_cached_msi_msg() start with a struct irq_data pointer,
look up the corresponding IRQ number, and pass it to get_cached_msi_msg(),
which then uses irq_get_irq_data() to look up the struct irq_data again to
call __get_cached_msi_msg().

Since we already have the struct irq_data, call __get_cached_msi_msg()
directly and skip the lookup work done by get_cached_msi_msg().

No functional change.

[bhelgaas: changelog]
Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: Tony Luck <tony.luck@intel.com>
CC: linux-ia64@vger.kernel.org