[init] Load uart and logger from initrd

Load drv.uart.elf and srv.logger.elf from the initrd and start them.
It's extremely manual and hard-coded at the moment, but it works and
they run, getting us back to where we were pre-initrd branch.

src/user/srv.init/init.module

@@ -5,10 +5,10 @@ init = module("srv.init",
     deps = [ "libc", "elf", "bootproto", "zstd" ],
     description = "Init server",
     sources = [
+        "j6romfs.cpp",
         "loader.cpp",
         "main.cpp",
         "modules.cpp",
-        "ramdisk.cpp",
         "service_locator.cpp",
         "start.s",
     ])