x32, siginfo: Provide proper overrides for x32 siginfo_t

Provide the proper override macros for x32 siginfo_t.  The combination
of a special type here and an overall alignment constraint actually
ends up with all the types being properly aligned, but the hack is
needed to keep the substructures inside siginfo_t from adding padding.

Note: use __attribute__((aligned())) since __aligned() is not exported
to user space.

[ v2: fix stray semicolon ]
Reported-by: NH.J. Lu <hjl.rools@gmail.com>
Cc: Bruce J. Beare <bruce.j.beare@intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Link: http://lkml.kernel.org/r/CAMe9rOqF6Kh6-NK7oP0Fpzkd4SBAWU%2BG53hwBbSD4iA2UzyxuA@mail.gmail.comSigned-off-by: NH. Peter Anvin <hpa@linux.intel.com>

arch/x86/include/asm/siginfo.h

@@ -2,7 +2,13 @@
 #define _ASM_X86_SIGINFO_H
 
 #ifdef __x86_64__
-# define __ARCH_SI_PREAMBLE_SIZE	(4 * sizeof(int))
+# ifdef __ILP32__ /* x32 */
+typedef long long __kernel_si_clock_t __attribute__((aligned(4)));
+#  define __ARCH_SI_CLOCK_T		__kernel_si_clock_t
+#  define __ARCH_SI_ATTRIBUTES		__attribute__((aligned(8)))
+# else /* x86-64 */
+#  define __ARCH_SI_PREAMBLE_SIZE	(4 * sizeof(int))
+# endif
 #endif
 
 #include <asm-generic/siginfo.h>