ui/egl-headless is only built when CONFIG_OPENGL is defined because it
depends on CONFIG_OPENGL without condition. Remove a redundant
conditonal in ui/egl-headless.c

Signed-off-by: Akihiko Odaki <akihiko.odaki@gmail.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20210714055646.85952-1-akihiko.odaki@gmail.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>