sp.c OK (#389)

* io/sp OK

* Fixed function prototype

* Made tharo's suggestions

src/libultra/io/sp.c

@@ -1,3 +1,10 @@
 #include "global.h"
 
-#pragma GLOBAL_ASM("asm/non_matchings/boot/sp/__osSpDeviceBusy.s")
+s32 __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 true;
+    }
+    return false;
+}