sh: sh7757: Add missing #include <asm/mmzone.h>

arch/sh/kernel/cpu/sh4a/setup-sh7757.c:1240:13: warning: no previous prototype for ‘plat_mem_setup’ [-Wmissing-prototypes]

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Link: https://lore.kernel.org/r/c9c26472151d16a2ca91f14bccd64af07a6abdd8.1709579038.git.geert+renesas@glider.be


Signed-off-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>