s390/ptrace: Explicitly include <linux/typecheck.h>

The psw_bits() macro makes use of typecheck() without that typecheck.h
is included. Add the missing include to avoid potential future compile
problems.

[hca@linux.ibm.com: change commit message]

Signed-off-by: Jens Remus <jremus@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

Author: Jens Remus

arch/s390/include/asm/ptrace.h

@@ -8,6 +8,7 @@
 #define _S390_PTRACE_H
 
 #include <linux/bits.h>
+#include <linux/typecheck.h>
 #include <uapi/asm/ptrace.h>
 #include <asm/thread_info.h>
 #include <asm/tpi.h>