target-arm: Fix intptr_t vs tcg_target_long

Fixes a build error when these are different, e.g. x32.

Signed-off-by: Richard Henderson <rth@twiddle.net>
Message-id: 1394043257-4800-1-git-send-email-rth@twiddle.net
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>