[PATCH] ppc64: Fix 64bit ptrace DABR support

Fix my stupid bug in the 64bit version of PTRACE_SET_DEBUGREG.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>