egl: move alloc & init out of _eglBuiltInDriver{DRI2,Haiku}

Note: dropping the EGL_BAD_ALLOC in egl_haiku because it's
overwritten by the EGL_NOT_INITIALIZED in eglInitialize().

Signed-off-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

src/egl/main/egldriver.c

@@ -52,8 +52,12 @@ _eglGetDriver(void)
 {
    mtx_lock(&_eglModuleMutex);
 
-   if (!_eglDriver)
-      _eglDriver = _eglBuiltInDriver();
+   if (!_eglDriver) {
+      _eglDriver = calloc(1, sizeof(*_eglDriver));
+      if (!_eglDriver)
+         return NULL;
+      _eglInitDriver(_eglDriver);
+   }
 
    mtx_unlock(&_eglModuleMutex);