ptrace: cleanup arch_ptrace() on score

Remove unnecessary castings.

Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Cc: Chen Liqin <liqin.chen@sunplusct.com>
Cc: Lennox Wu <lennox.wu@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>