Rename `func_80089C50` to `nuGfxDisplayOn` and move it into it's own C file

linker_scripts/symbols/addr.txt

@@ -52,6 +52,7 @@ nuGfxTaskAllEndWait = 0x80089A10;
 nuGfxTaskMgr = 0x80089540;
 nuGfxFuncSet = 0x80089990;
 nuGfxDisplayOff = 0x80089BC0;
+nuGfxDisplayOn = 0x80089C50;
 
 
 obCurrentTime = 0x800C47D0;

splat.yaml

@@ -120,7 +120,8 @@ segments:
       - [0x19E30, c, "nu/nugfxretracewait"]
       - [0x19EB0, c, "nu/nugfxsetcfb"]
       - [0x19FC0, c, "nu/nugfxdisplayoff"]
-      - [0x1A050, c, "_ob_icy_coast"]
+      - [0x1A050, c, "nu/nugfxdisplayon"]
+      - [0x1A060, c, "_ob_icy_coast"]
       - [0x1A4F0, c, "rom_copy"]
       - [0x1A5B0, c, "_ob_unusual_spiders"]
       - [0x1A660, c, "_ob_prized_reading"]

src/_ob_icy_coast.c

@@ -1,11 +1,5 @@
 #include "common.h"
 
-#include "nu/nusys.h"
-
-void func_80089C50(void) {
-    nuGfxDisplay = NU_GFX_DISPLAY_ON_TRIGGER;
-}
-
 /* 1A060 80089C60 */
 u8 obControllerInit(void) {
     u8 pattern;

src/nu/nugfxdisplayon.c

@@ -0,0 +1,7 @@
+#include "common.h"
+
+#include "nu/nusys.h"
+
+void nuGfxDisplayOn(void) {
+    nuGfxDisplay = NU_GFX_DISPLAY_ON_TRIGGER;
+}