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_code_O2/sp.c

@@ -1,11 +1,10 @@
 #include "global.h"
 
-u32 __osSpDeviceBusy() {
+u32 __osSpDeviceBusy(void) {
     register u32 status = HW_REG(SP_STATUS_REG, u32);
 
     if (status & (SP_STATUS_DMA_BUSY | SP_STATUS_DMA_FULL | SP_STATUS_IO_FULL)) {
         return 1;
     }
-
     return 0;
 }