m68k/mac: Remove unneeded linux/miscdevice.h include

arch/m68k/mac/misc.c does not use any miscdevice so the
inclusion of linux/miscdevice.h is unnecessary.
This patch remove this unnecessary include.

Signed-off-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>