[SPARC64]: Fix several bugs in MSI handling.

1) sun4{u,v}_build_msi() have improper return value handling.

   We should always return negative error codes, instead of
   using the magic value "0" which could in fact be a valid
   MSI number.

2) sun4{u,v}_build_msi() should return -ENOMEM instead of
   calling prom_prom() halt with kzalloc() of the interrupt
   data fails.

3) We 'remembered' the MSI number using a singleton in the
   struct device archdata area, this doesn't work for MSI-X
   which can cause multiple MSIs assosciated with one device.

   Delete that archdata member, and instead store the MSI
   number in the IRQ chip data area.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/asm-sparc64/irq.h b/include/asm-sparc64/irq.h
index c041e10..c00ad15 100644
--- a/include/asm-sparc64/irq.h
+++ b/include/asm-sparc64/irq.h
@@ -53,6 +53,9 @@
 extern void sun4v_destroy_msi(unsigned int virt_irq);
 extern unsigned int sbus_build_irq(void *sbus, unsigned int ino);
 
+extern void sparc64_set_msi(unsigned int virt_irq, u32 msi);
+extern u32 sparc64_get_msi(unsigned int virt_irq);
+
 extern void fixup_irqs(void);
 
 static __inline__ void set_softint(unsigned long bits)