st/omx/bellagio: Rename st and target directories

v2: Refactor out screen functions to st/omx

Allows to keep all the code under st/omx (st/omx/tizonia and
st/omx/bellagio).
Reverts targets/omx_bellagio to omx as additions to existing files
is enough to compile for both bellagio and tizonia.

* autotools changes:
  --enable-omx -> --enable-omx-bellagio

* meson changes:
  -Dgallium-omx=false -> -Dgallium-omx=disabled
  -Dgallium-omx=true  -> -Dgallium-omx=bellagio

Acked-by: Leo Liu <leo.liu@amd.com>
Reviewed-by: Julien Isorce <julien.isorce@gmail.com>

meson.build

@@ -464,29 +464,28 @@ endif
 
 _omx = get_option('gallium-omx')
 if not system_has_kms_drm
-  if _omx == 'true'
+  if _omx != 'disabled'
     error('OMX state tracker can only be built on unix-like OSes.')
   else
-    _omx = 'false'
+    _omx = 'disabled'
   endif
 elif not (with_platform_x11 or with_platform_drm)
-  if _omx == 'true'
+  if _omx != 'disabled'
     error('OMX state tracker requires X11 or drm platform support.')
   else
-    _omx = 'false'
+    _omx = 'disabled'
   endif
 elif not (with_gallium_r600 or with_gallium_radeonsi or with_gallium_nouveau)
-  if _omx == 'true'
+  if _omx != 'disabled'
     error('OMX state tracker requires at least one of the following gallium drivers: r600, radeonsi, nouveau.')
   else
-    _omx = 'false'
+    _omx = 'disabled'
   endif
-elif _omx == 'auto'
-  _omx = 'true'
 endif
-with_gallium_omx = _omx == 'true'
+with_gallium_omx = _omx != 'disabled'
+gallium_omx = _omx
 dep_omx = []
-if with_gallium_omx
+if gallium_omx == 'bellagio'
   dep_omx = dependency('libomxil-bellagio')
 endif