microblaze: clean up signal handling

When legacy signal handling is disabled, the
arch/microblaze/kernel/signal.c implementation can
be much simpler, as most of it is handled generically
from kernel/signal.c.

This is also a prerequisite for using the generic
asm/unistd.h, which does not provide __NR_sigreturn,
because this macro is referenced by the current signal.c
implementation.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Michal Simek <monstr@monstr.eu>
diff --git a/arch/microblaze/kernel/syscall_table.S b/arch/microblaze/kernel/syscall_table.S
index 376d178..ef0e893 100644
--- a/arch/microblaze/kernel/syscall_table.S
+++ b/arch/microblaze/kernel/syscall_table.S
@@ -71,12 +71,12 @@
 	.long sys_getppid
 	.long sys_getpgrp		/* 65 */
 	.long sys_setsid
-	.long sys_sigaction
+	.long sys_ni_syscall		/* sys_sigaction */
 	.long sys_sgetmask
 	.long sys_ssetmask
 	.long sys_setreuid		/* 70 */
 	.long sys_setregid
-	.long sys_sigsuspend_wrapper
+	.long sys_ni_syscall		/* sys_sigsuspend_wrapper */
 	.long sys_sigpending
 	.long sys_sethostname
 	.long sys_setrlimit		/* 75 */
@@ -123,7 +123,7 @@
 	.long sys_sysinfo
 	.long sys_ipc
 	.long sys_fsync
-	.long sys_sigreturn_wrapper
+	.long sys_ni_syscall		/* sys_sigreturn_wrapper */
 	.long sys_clone_wrapper		/* 120 */
 	.long sys_setdomainname
 	.long sys_newuname