parisc: Fix __ARCH_SI_PREAMBLE_SIZE on parisc

On a 64bit kernel build the compiler aligns the _sifields union in the struct siginfo_t on a 64bit address. The __ARCH_SI_PREAMBLE_SIZE define compensates for this alignment and thus fixes the wait testcase of the strace package.

The symptoms of a wrong __ARCH_SI_PREAMBLE_SIZE value is that _sigchld.si_stime variable is missed to be copied and thus after a copy_siginfo() will have uninitialized values.

index d703472..1c75565 100644
@@ -1,6 +1,10 @@
 #ifndef _PARISC_SIGINFO_H
 #define _PARISC_SIGINFO_H
 
+#if defined(__LP64__)
+#define __ARCH_SI_PREAMBLE_SIZE   (4 * sizeof(int))
+#endif
+
 #include <asm-generic/siginfo.h>
 
 #undef NSIGTRAP