misc: C2port needs <linux/sched.h>

m68k allmodconfig:

| drivers/misc/c2port/core.c: In function 'c2port_reset':
| drivers/misc/c2port/core.c:73: error: dereferencing pointer to incomplete type
| drivers/misc/c2port/core.c: In function 'c2port_strobe_ck':
| drivers/misc/c2port/core.c:91: error: dereferencing pointer to incomplete type

Include <linux/sched.h> to fix it, as m68k's local_irq_enable() needs to know
about struct task_struct.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>