target/riscv/pmp: Fix integer overflow in TOR and NA4 address computation

According to the RISC-V Privileged Manual: "The Sv32 page-based virtual-memory scheme described in sv32 supports 34-bit physical addresses for RV32, so the PMP scheme must support addresses wider than XLEN for RV32." However, the current QEMU implementation uses `target_ulong` (which resolves to `uint32_t` on RV32) for PMP address variables. When shifting these addresses left (e.g., `this_addr << 2`), an integer overflow occurs, truncating the high bits of the 34-bit physical address. Fix this issue by changing the types of PMP address variables (`this_addr` and `prev_addr`) to `hwaddr`. This issue was discovered and reported by SpecHunter, an AI-driven architecture specification analysis tool. Link: https://github.com/yizishun/rv-isa-sec/blob/master/output/riscv-isa-manual/pr-2472/qemu.txt Signed-off-by: Zishun Yi <vulab@iscas.ac.cn> Reviewed-by: Alistair Francis <alistair.francis@wdc.com> Reviewed-by: Daniel Henrique Barboza <daniel.barboza@oss.qualcomm.com> Message-ID: <20260511102627.3120140-1-vulab@iscas.ac.cn> Signed-off-by: Alistair Francis <alistair.francis@wdc.com>