microblaze: Fix sparse warnings - ptrace

Warning log:
CHECK   arch/microblaze/kernel/ptrace.c
arch/microblaze/kernel/ptrace.c:126:11: warning: incorrect type in initializer (different address spaces)
arch/microblaze/kernel/ptrace.c:126:11:    expected unknown type 2[noderef] *__pu_addr<asn:1>
arch/microblaze/kernel/ptrace.c:126:11:    got unsigned long *<noident>
arch/microblaze/kernel/ptrace.c:134:17: warning: symbol 'do_syscall_trace_enter' was not declared. Should it be static?
arch/microblaze/kernel/ptrace.c:157:17: warning: symbol 'do_syscall_trace_leave' was not declared. Should it be static?

Signed-off-by: Michal Simek <monstr@monstr.eu>
diff --git a/arch/microblaze/include/asm/syscall.h b/arch/microblaze/include/asm/syscall.h
index 048dfcd..9bc4317 100644
--- a/arch/microblaze/include/asm/syscall.h
+++ b/arch/microblaze/include/asm/syscall.h
@@ -96,4 +96,7 @@
 		microblaze_set_syscall_arg(regs, i++, *args++);
 }
 
+asmlinkage long do_syscall_trace_enter(struct pt_regs *regs);
+asmlinkage void do_syscall_trace_leave(struct pt_regs *regs);
+
 #endif /* __ASM_MICROBLAZE_SYSCALL_H */