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/libultra_boot_O2/osPiGetCmdQueue.c

@@ -1,7 +1,7 @@
 #include "global.h"
 #include "ultra64/internal.h"
 
-OSMesgQueue* osPiGetCmdQueue() {
+OSMesgQueue* osPiGetCmdQueue(void) {
     if (!__osPiDevMgr.initialized) {
         return NULL;
     }