arm: switch to GENERIC_PCI_IOMAP

arm copied pci_iomap from generic code, probably to avoid
pulling the rest of iomap.c in.  Since that's in
a separate file now, we can reuse the common implementation.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 44789ef..2ebf66b 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -30,6 +30,7 @@
 	select HAVE_SPARSE_IRQ
 	select GENERIC_IRQ_SHOW
 	select CPU_PM if (SUSPEND || CPU_IDLE)
+	select GENERIC_PCI_IOMAP
 	help
 	  The ARM series is a line of low-power-consumption RISC chip designs
 	  licensed by ARM Ltd and targeted at embedded applications and