arch/tile: avoid erroneous error return for PTRACE_POKEUSR.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
diff --git a/arch/tile/kernel/ptrace.c b/arch/tile/kernel/ptrace.c
index e5701d1..7161bd0 100644
--- a/arch/tile/kernel/ptrace.c
+++ b/arch/tile/kernel/ptrace.c
@@ -96,6 +96,7 @@
 		if (addr < 0 || addr >= PTREGS_SIZE)
 			break;
 		putreg(child, addr, data);   /* Write register */
+		ret = 0;
 		break;
 
 	case PTRACE_GETREGS:  /* Get all registers from the child. */