egl: Untangle some spaghetti around _eglLookupDisplay

Only eglapi needs any of this.

Reviewed-by: Eric Engestrom <eric@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18713>

src/egl/main/egldisplay.h

@@ -254,28 +254,10 @@ extern void
 _eglCleanupDisplay(_EGLDisplay *disp);
 
 
-extern EGLBoolean
-_eglCheckDisplayHandle(EGLDisplay dpy);
-
-
 extern EGLBoolean
 _eglCheckResource(void *res, _EGLResourceType type, _EGLDisplay *disp);
 
 
-/**
- * Lookup a handle to find the linked display.
- * Return NULL if the handle has no corresponding linked display.
- */
-static inline _EGLDisplay *
-_eglLookupDisplay(EGLDisplay dpy)
-{
-   _EGLDisplay *disp = (_EGLDisplay *) dpy;
-   if (!_eglCheckDisplayHandle(dpy))
-      disp = NULL;
-   return disp;
-}
-
-
 /**
  * Return the handle of a linked display, or EGL_NO_DISPLAY.
  */