lib/plist.c: remove redundant include

Removing the include of linux/spinlock.h produces byte-identical output
for {allno,def}config, and identical objdump -d output for allyesconfig.
In the former two cases, more than a 100 lines are eliminated from the
generated dependency file.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/plist.c

@@ -25,7 +25,6 @@
 
 #include <linux/bug.h>
 #include <linux/plist.h>
-#include <linux/spinlock.h>
 
 #ifdef CONFIG_DEBUG_PI_LIST