x86: Include types.h explicitly in the i386 version of io.h

The i386 version of io.h depends on the phys_addr_t type which is defined in
types.h. It wasn't including that explicitly, and was working presumably
because the other files including it had already included types.h themselves
directly or indirectly. This change fixes that.

Signed-off-by: Gabe Black <gabeblack@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>