[POWERPC] Rename prom_n_addr_cells to of_n_addr_cells

This is more consistent and gets us closer to the Sparc code.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/platforms/pseries/xics.c b/arch/powerpc/platforms/pseries/xics.c
index 81d172d..f0795fa 100644
--- a/arch/powerpc/platforms/pseries/xics.c
+++ b/arch/powerpc/platforms/pseries/xics.c
@@ -643,7 +643,7 @@
 		addrp = get_property(np, "8259-interrupt-acknowledge", NULL);
 		if (addrp == NULL)
 			continue;
-		naddr = prom_n_addr_cells(np);
+		naddr = of_n_addr_cells(np);
 		intack = addrp[naddr-1];
 		if (naddr > 1)
 			intack |= ((unsigned long)addrp[naddr-2]) << 32;