egl: Remove unused driver and display functions.

Remove _eglPreloadDriver, _eglLookupDriver, and _eglSplitDisplayString.

src/egl/main/egldisplay.h

@@ -58,10 +58,6 @@ extern void
 _eglFiniDisplay(void);
 
 
-extern char *
-_eglSplitDisplayString(const char *dpyString, const char **args);
-
-
 extern _EGLDisplay *
 _eglNewDisplay(NativeDisplayType displayName);