"exec/address-spaces.h" declares get_system_io() and
get_system_memory(), both returning a MemoryRegion pointer.
MemoryRegion is forward declared in "qemu/typedefs.h", so
we don't need any declaration from "exec/memory.h" here.
Remove it.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230619074153.44268-4-philmd@linaro.org>