hw/dma/etraxfs: Include missing 'exec/memory.h' header

hw/dma/etraxfs: Include missing 'exec/memory.h' header

The 'fs_dma_ctrl' structure has a MemoryRegion 'mmio' field
which is initialized in etraxfs_dmac_init() calling
memory_region_init_io() and memory_region_add_subregion().

These functions are declared in "exec/memory.h", along with
the MemoryRegion structure. Include the missing header.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230619074153.44268-3-philmd@linaro.org>