target/arm: fix stage 2 page-walks in 32-bit emulation

Using a target unsigned long would limit the Input Address to a LPAE
page-walk to 32 bits on AArch32 and 64 bits on AArch64. This is okay
for stage 1 or on AArch64, but it is insufficient for stage 2 on
AArch32. In that later case, the Input Address can have up to 40 bits.

Signed-off-by: Rémi Denis-Courmont <remi.denis.courmont@huawei.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20201118150414.18360-1-remi@remlab.net
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>