[boot] Save size of program in its module

Init will eventually want to know the full size of the program the
bootloader passed it, so save this off in the module_program struct.

src/boot/loader.cpp

@@ -43,6 +43,7 @@ create_module(buffer data, const program_desc &desc, bool loaded)
     init::module_program *mod = g_alloc.allocate_module<init::module_program>(path_len);
     mod->mod_type = init::module_type::program;
     mod->base_address = reinterpret_cast<uintptr_t>(data.pointer);
+    mod->size = data.count;
     if (loaded)
         mod->mod_flags = static_cast<init::module_flags>(
             static_cast<uint8_t>(mod->mod_flags) |

src/include/init_args.h

@@ -34,6 +34,7 @@ struct module_program :
     public module
 {
     uintptr_t base_address;
+    size_t size;
     char filename[];
 };