ui/egl: fix make_context_current() callback return value

ui/egl: fix make_context_current() callback return value

eglMakeCurrent() returns 1/EGL_TRUE on success. This is not what the
callback expects, where 0 indicates success.

While at it, print the EGL error to ease debugging.

As with virgl_renderer_callbacks, the return value is now checked since
version >= 4:
https://gitlab.freedesktop.org/virgl/virglrenderer/-/commit/7f09e6bf0c6ceea6727bd0049781256a28cab0e5

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20230606115658.677673-3-marcandre.lureau@redhat.com>