Shrink struct task_struct::oomkilladj

oomkilladj is int, but values which can be assigned to it are -17, [-16,
15], thus fitting into s8.

While patch itself doesn't help in making task_struct smaller, because of
natural alignment of ->link_count, it will make picture clearer wrt futher
task_struct reduction patches.  My plan is to move ->fpu_counter and
->oomkilladj after ->ioprio filling hole on i386 and x86_64.  But that's
for later, because bloated distro configs need looking at as well.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/sched.h

@@ -1010,7 +1010,7 @@ struct task_struct {
 	 * a short time
 	 */
 	unsigned char fpu_counter;
-	int oomkilladj; /* OOM kill score adjustment (bit shift). */
+	s8 oomkilladj; /* OOM kill score adjustment (bit shift). */
 	char comm[TASK_COMM_LEN]; /* executable name excluding path
 				     - access with [gs]et_task_comm (which lock
 				       it with task_lock())