parisc: fix double restarts

Don't bother restoring r28 on syscall restarts; it's clobbered by
syscall anyway.  Reuse (now unused) ->orig_r28 as "no restarts allowed"
flag.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/parisc/hpux/gate.S b/arch/parisc/hpux/gate.S
index 38a1c1b..0114688 100644
--- a/arch/parisc/hpux/gate.S
+++ b/arch/parisc/hpux/gate.S
@@ -71,7 +71,7 @@
 	STREG	%r26, TASK_PT_GR26(%r1)	 	/* 1st argument */
 	STREG	%r27, TASK_PT_GR27(%r1)		/* user dp */
 	STREG   %r28, TASK_PT_GR28(%r1)         /* return value 0 */
-	STREG   %r28, TASK_PT_ORIG_R28(%r1)     /* return value 0 (saved for signals) */
+	STREG   %r0, TASK_PT_ORIG_R28(%r1)     /* don't prohibit restarts */
 	STREG   %r29, TASK_PT_GR29(%r1)         /* 8th argument */
 	STREG	%r31, TASK_PT_GR31(%r1)		/* preserve syscall return ptr */