ui/gtk-egl: un-tab and re-tab should destroy egl surface and context

An old esurface should be destroyed and set to be NULL when doing
un-tab and re-tab so that a new esurface an context can be created
for the window widget that those will be bound to.

v2: enabling opengl specific routines only when CONFIG_OPENGL is set

Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Dongwon Kim <dongwon.kim@intel.com>
Signed-off-by: Khairul Anuar Romli <khairul.anuar.romli@intel.com>
Message-Id: <20211104065153.28897-1-dongwon.kim@intel.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>