sched: Fix compiler warnings

Gcc-4.8 issues some pointer type cast warnings.
Fix them.

kernel/kernel/sched/core.c: In function 'try_to_wake_up':
kernel/kernel/sched/core.c:1548:14: warning: cast to pointer from integer of
different size [-Wint-to-pointer-cast]
error, forbidden warning: core.c:1548
make[4]: *** [kernel/sched/core.o] Error 1
make[3]: *** [kernel/sched] Error 2
make[3]: *** Waiting for unfinished jobs....

Change-Id: I1808b435a0e6fdeacac7b8842a80452825205303
Signed-off-by: Abhimanyu Kapur <abhimany@codeaurora.org>