headers: prctl.h -- Add missing linux/types.h

Stephen reported:

 | After merging the akpm-current tree, today's linux-next build (x86_64
 | allmodconfig) failed like this:
 |
 | ./usr/include/linux/prctl.h:132: found __[us]{8,16,32,64} type without #include <linux/types.h>
 | In file included from /usr/include/x86_64-linux-gnu/sys/prctl.h:23:0,
 |                 from Documentation/prctl/disable-tsc-test.c:14:
 | ./usr/include/linux/prctl.h:132:2: error: unknown type name '__u64'
 |

Include the header needed.

---
 include/uapi/linux/prctl.h |    2 ++
 1 file changed, 2 insertions(+)

Index: linux-2.6.git/include/uapi/linux/prctl.h
===================================================================
@@ -1,6 +1,8 @@
 #ifndef _LINUX_PRCTL_H
 #define _LINUX_PRCTL_H
 
+#include <linux/types.h>
+
 /* Values to pass as first argument to prctl() */
 
 #define PR_SET_PDEATHSIG  1  /* Second arg is a signal */