hw/arm/raspi4b: fix guest never seeing more than ~1 GiB of RAM

raspi4_modify_dtb() decides whether to add a second memory node above the 1 GiB peripheral hole by checking info->ram_size -- but that field is the boot loader's RAM budget for loading the kernel/initrd/dtb image, itself always capped to at most UPPER_RAM_BASE - vcram_size by raspi_base_machine_init(). Since that capped value can never exceed UPPER_RAM_BASE by construction, the condition was never true for any raspi4b configuration, and the second node was never added: the guest never saw more than ~1 GiB of its nominal RAM, regardless of the machine's actual size. board_ram_size(info->board_id), computed one line above in the same function, is the value that was actually needed -- the board's real total RAM, not the boot loader's own budget for where it's allowed to place the kernel image. Confirmed via direct measurement inside the guest ("free -h" / /proc/meminfo) on raspi4b's default 2 GiB configuration, before and after: before: MemTotal: 943524 kB (~921 MiB) after: MemTotal: 1905824 kB (~1861 MiB) Also verified against two real, unmodified Raspberry Pi OS releases (Debian 11/Bullseye and Debian 13/Trixie): both now report ~1.8 GiB of usable RAM instead of ~900 MiB, with clean boots, working SSH, and no kernel errors on either. Signed-off-by: Marcelo Manzo <marcelomanzo@gmail.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@oss.qualcomm.com> Message-id: 20260811143539.7835-2-marcelomanzo@gmail.com Signed-off-by: Peter Maydell <peter.maydell@linaro.org>