[PARISC] Fix some compile problems in ptrace.c

Fix some compile problems:
- ret wasn't being initialised in all code paths
- I'm pretty sure 'goto out' should have been 'goto out_tsk'

Signed-off-by: Matthew Wilcox <willy@parisc-linux.org>
Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>