ptrace: cleanup arch_ptrace() on cris

Use new 'regno' variable in order to remove redandunt expression and
remove checking @addr less than 0 because @addr is now unsigned.  Also
update 'datap' on PTRACE_GET/SETREGS to fix a bug on arch-v10.

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Acked-by: Mikael Starvik <starvik@axis.com>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>