include/linux/genalloc.h: spinlock_t needs spinlock_types.h

Compiling a C file which includes genalloc.h but without
spinlock_types.h being included before, we will see the compile error
below.

 include/linux/genalloc.h:54:2: error: unknown type name `spinlock_t'

Include spinlock_types.h from genalloc.h to fix the problem.
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/genalloc.h

@@ -30,6 +30,8 @@
 #ifndef __GENALLOC_H__
 #define __GENALLOC_H__
 
+#include <linux/spinlock_types.h>
+
 struct device;
 struct device_node;