powerpc: Use is_kdump_kernel()

linux/crash_dump.h defines is_kdump_kernel() to be used by code that
needs to know if the previous kernel crashed instead of a (clean) boot
or reboot.

This updates the just added powerpc code to use it.  This is needed
for the next commit, which will remove __kdump_flag.

Signed-off-by: Milton Miller <miltonm@bga.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/platforms/pseries/iommu.c

@@ -32,6 +32,7 @@
 #include <linux/string.h>
 #include <linux/pci.h>
 #include <linux/dma-mapping.h>
+#include <linux/crash_dump.h>
 #include <asm/io.h>
 #include <asm/prom.h>
 #include <asm/rtas.h>
@@ -44,7 +45,6 @@
 #include <asm/tce.h>
 #include <asm/ppc-pci.h>
 #include <asm/udbg.h>
-#include <asm/kdump.h>
 
 #include "plpar_wrappers.h"
 
@@ -292,7 +292,7 @@ static void iommu_table_setparms(struct pci_controller *phb,
 
 	tbl->it_base = (unsigned long)__va(*basep);
 
-	if (!__kdump_flag)
+	if (!is_kdump_kernel())
 		memset((void *)tbl->it_base, 0, *sizep);
 
 	tbl->it_busno = phb->bus->number;