MIPS: uapi/asm/siginfo.h: Fix GCC 4.1.2 compilation

It wasn't until GCC 4.3 I believe that the __SIZEOF_*__ predefined macros
were added.  The change below switches <uapi/asm/siginfo.h> to the
_MIPS_SZLONG macro so that compilation with e.g. GCC 4.1.2 succeeds.
This is a user API header so I think this is even more important, for
older userland support.  The change adds an unsuccessful default too, to
catch any compiler configuration oddities.
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/5630/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/uapi/asm/siginfo.h

@@ -25,11 +25,12 @@ struct siginfo;
 /*
  * Careful to keep union _sifields from shifting ...
  */
-#if __SIZEOF_LONG__ == 4
+#if _MIPS_SZLONG == 32
 #define __ARCH_SI_PREAMBLE_SIZE (3 * sizeof(int))
-#endif
-#if __SIZEOF_LONG__ == 8
+#elif _MIPS_SZLONG == 64
 #define __ARCH_SI_PREAMBLE_SIZE (4 * sizeof(int))
+#else
+#error _MIPS_SZLONG neither 32 nor 64
 #endif
 
 #include <asm-generic/siginfo.h>