arch/tile: Fix a couple of issues with the COMPAT code for TILE-Gx.

First, the siginfo preamble wasn't quite right; we need to indicate
that we are padding up to 4 ints of preamble for 64-bit code, and
then for compat mode we need to pad differently, using only 3 ints.

Second, the C ABI requires a save area of two registers, not two
pointers, since in compat mode we have 64-bit registers all of which
we need to save, even though we only have 32-bit VAs.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

arch/tile/include/asm/siginfo.h

@@ -17,6 +17,10 @@
 
 #define __ARCH_SI_TRAPNO
 
+#ifdef __LP64__
+# define __ARCH_SI_PREAMBLE_SIZE	(4 * sizeof(int))
+#endif
+
 #include <asm-generic/siginfo.h>
 
 /*