ahci msi_map with fallback

[Kenneth R Westerback]

Try msi and fallback to old intr mapping. Works on my box where the
ahci is on a non-msi bus.

ok?

.... Ken

Index: ahci.c
===================================================================
RCS file: /cvs/src/sys/dev/pci/ahci.c,v
retrieving revision 1.178
diff -u -p -r1.178 ahci.c
--- ahci.c      8 May 2011 19:46:10 -0000       1.178
+++ ahci.c      1 Jun 2011 14:53:05 -0000
@@ -762,7 +762,7 @@ ahci_pci_attach(struct device *parent, s
                }
        }
 
-       if (pci_intr_map(pa, &ih) != 0) {
+       if (pci_intr_map_msi(pa, &ih) != 0 && pci_intr_map(pa, &ih) != 0) {
                printf(": unable to map interrupt\n");
                return;
        }