MN10300: Use asm-generic/pci_iomap.h

The declarations from MN10300's pci_iomap() was removed by commit
34f1bdee1910f7efe3c32e1a891dba4fd21cb3b6 but asm-generic/pci_iomap.h wasn't
then #included from asm/io.h.

Signed-off-by: David Howells <dhowells@redhat.com>

arch/mn10300/include/asm/io.h

@@ -14,6 +14,7 @@
 #include <asm/page.h> /* I/O is all done through memory accesses */
 #include <asm/cpu-regs.h>
 #include <asm/cacheflush.h>
+#include <asm-generic/pci_iomap.h>
 
 #define mmiowb() do {} while (0)