STM32H747: general M4 fixes

[facchinm]

Should fix #772 (see #741 (comment) ).

Coexistence between M4 and M7 got broken by #741 , alongside printf functionality in M4 (sicne default console is not defined anymore)

@Bexin3 can you test with your project? I tried it and it seems to work but the tearing is "important" (and it's not a regression as far as I can tell)

[Bexin3]

I will test this in a few hours when I am back home.
Regarding the tearing, that one also happened in older versions, but it wasn't fixed which I thing some of the update notes mentioned it should be fixed. The tearing is a vertical stripe, and its not a vsync issue but particles appear on both sides of the tear, similar behaviour sometimes happened when I had an incorrect if function writing into a buffer, for some reason pixels would sometimes jump over the place. I think that the tear leaves some pixels unapdates on both sides while some get updated but honestly I can't say for certain, I can take a photo when home.

[Bexin3]

Is there anywhere I could get this compiled? I am afraid I am not really good at understanding compilation stuff and so far failed to compile this.