hw/elf_ops.h: switch to ssize_t for elf loader return type

hw/elf_ops.h: switch to ssize_t for elf loader return type

Until now, int was used as the return type for all the ELF
loader related functions. The returned value is the sum of all loaded
program headers "MemSize" fields.

Because of the overflow check in elf_ops.h, trying to load an ELF bigger
than INT_MAX will fail. Switch to ssize_t to remove this limitation.

Signed-off-by: Luc Michel <lmichel@kalray.eu>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Message-Id: <20211014194325.19917-1-lmichel@kalray.eu>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>