tile: fix bug in get_user() for 4-byte values

The definition of 32-bit values in the 64-bit tilegx architecture is that
they should be sign-extended regardless of whether they are considered
signed or unsigned by the compiler.  Accordingly, we need to use an
"ld4s" rather than "ld4u" to load and sign-extend for get_user().

This fixes glibc bug 14238 (see http://sourceware.org/bugzilla),
introduced during the 3.5 merge window.
Signed-off-by: NChris Metcalf <cmetcalf@tilera.com>

arch/tile/include/asm/uaccess.h

@@ -146,7 +146,7 @@ extern int fixup_exception(struct pt_regs *regs);
 #ifdef __tilegx__
 #define __get_user_1(x, ptr, ret) __get_user_asm(ld1u, x, ptr, ret)
 #define __get_user_2(x, ptr, ret) __get_user_asm(ld2u, x, ptr, ret)
-#define __get_user_4(x, ptr, ret) __get_user_asm(ld4u, x, ptr, ret)
+#define __get_user_4(x, ptr, ret) __get_user_asm(ld4s, x, ptr, ret)
 #define __get_user_8(x, ptr, ret) __get_user_asm(ld, x, ptr, ret)
 #else
 #define __get_user_1(x, ptr, ret) __get_user_asm(lb_u, x, ptr, ret)