xtensa: switch to generic sigaltstack

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/xtensa/include/uapi/asm/unistd.h b/arch/xtensa/include/uapi/asm/unistd.h
index 5162418..19fac3f 100644
--- a/arch/xtensa/include/uapi/asm/unistd.h
+++ b/arch/xtensa/include/uapi/asm/unistd.h
@@ -483,7 +483,7 @@
 #define __NR_restart_syscall 			223
 __SYSCALL(223, sys_restart_syscall, 0)
 #define __NR_sigaltstack 			224
-__SYSCALL(224, xtensa_sigaltstack, 2)
+__SYSCALL(224, sys_sigaltstack, 2)
 #define __NR_rt_sigreturn 			225
 __SYSCALL(225, xtensa_rt_sigreturn, 1)
 #define __NR_rt_sigaction 			226