um: io.h: include <linux/types.h>

This may be needed for size_t if something doesn't get
it included elsewhere before including <asm/io.h>, so
add the include.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/include/asm/io.h

 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef _ASM_UM_IO_H
 #define _ASM_UM_IO_H
+#include <linux/types.h>
 
 #define ioremap ioremap
 static inline void __iomem *ioremap(phys_addr_t offset, size_t size)