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/osViGetNextFramebuffer.c

@@ -1,8 +1,9 @@
 #include "global.h"
 
-void* osViGetNextFramebuffer() {
+void* osViGetNextFramebuffer(void) {
     s32 prevInt = __osDisableInt();
     void* buff = __osViNext->buffer;
+
     __osRestoreInt(prevInt);
     return buff;
 }