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/sys_math.c

@@ -17,7 +17,7 @@ f32 Math_Factorial(s32 n) {
     f32 ret;
     s32 i;
 
-    if (n > 12U) {
+    if ((u32)n > 12U) {
         ret = sFactorialTbl[12];
         for (i = 13; i <= n; i++) {
             ret *= i;