Undo duplicate "m68k: drivers/input/serio/hp_sdc.c needs <linux/semaphore.h>"

Both commits 0f17e4c7 ("Add missing
semaphore.h includes") and 4933d075
("m68k: drivers/input/serio/hp_sdc.c needs <linux/semaphore.h>") added a

We only really need one ;)

Reported-by: Huang Weiyi <weiyi.huang@gmail.com>
Requested-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>