Screeninit issues in latest prerelease

[aspargas2]

As of commit b6b4693 (meaning this affects the latest pre-release), this firm's screen initialization is broken. When chainloading from boot9strap or GodMode9 (v2.0.0) this results in a black screen with the backlight on. When chainloading from Luma3DS (v10.2.1), this results in garbage on both screens. When chainloading from Fastboot3DS (v1.2), this results in this effect.

In all of these cases, the firm is still completely functional aside from visuals, and the screen problems go away once linux itself is loaded and takes control of the screens. The cause of this may be related to the cause of this GodMode9 issue, but if I recall correctly the specific behavior of that one was a bit different.

[Wolfvak]

for posteriority, the part about clearing the screen garbage is related to #5