ARM64: use GENERIC_PCI_IOMAP

Patch 09a5723983 ("arm64: Use include/asm-generic/io.h") correctly
removed the GENERIC_IOMAP selection from ARM64, which is not needed
on architectures that have memory-mapped PCI I/O space, however
we now lack a pci_iomap() function.

Fortunately, there is already a generic implementation for this
case, so we just need to select GENERIC_PCI_IOMAP to make it all
work.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 09a5723983 ("arm64: Use include/asm-generic/io.h")

arch/arm64/Kconfig

@@ -25,6 +25,7 @@ config ARM64
 	select GENERIC_EARLY_IOREMAP
 	select GENERIC_IRQ_PROBE
 	select GENERIC_IRQ_SHOW
+	select GENERIC_PCI_IOMAP
 	select GENERIC_SCHED_CLOCK
 	select GENERIC_SMP_IDLE_THREAD
 	select GENERIC_STRNCPY_FROM_USER