[boot] Seperate video out from console

Separate the video mode setting out from the console code into video.*,
and remove the framebuffer from the kernel args, moving it to the new
init args format.

src/boot/module.toml

@@ -16,4 +16,5 @@ sources = [
 	"paging.cpp",
 	"status.cpp",
 	"support.cpp",
+	"video.cpp",
 ]