Fix most compiler warnings in the boot and code segments (#674)

* Less warnings in boot & code segments

* few more warnings gone

* Ran formatter

* z_view warning gone

* -> 1

* f31 -> 31

* Remove function casts

* Few more small improvements

* Separate declaration and assignment in func_80091738 and Item_Give

Co-authored-by: Thar0 <maximilianc64@gmail.com>

src/code/code_800ACE70.c

@@ -65,9 +65,7 @@ void func_800ACE90(struct_801664F0* this) {
 
 // Draw
 void func_800ACE98(struct_801664F0* this, Gfx** gfxp) {
-    Gfx* gfx;
-
-    gfx = *gfxp;
+    Gfx* gfx = *gfxp;
 
     gDPPipeSync(gfx++);
     gDPSetPrimDepth(gfx++, -1, -1);