powerpc: Add asm/syscall.h with the tracehook entry points

Add asm/syscall.h for powerpc with all the required entry points.
This will allow arch-independent tracing code for system calls.

BenH: Fixed up use of regs->trap to properly mask low bit

Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/include/asm-powerpc/ptrace.h b/include/asm-powerpc/ptrace.h
index 3d6e310..734e075 100644
--- a/include/asm-powerpc/ptrace.h
+++ b/include/asm-powerpc/ptrace.h
@@ -84,6 +84,7 @@
 #ifndef __ASSEMBLY__
 
 #define instruction_pointer(regs) ((regs)->nip)
+#define user_stack_pointer(regs) ((regs)->gpr[1])
 #define regs_return_value(regs) ((regs)->gpr[3])
 
 #ifdef CONFIG_SMP