cogl-buffer: fix compilation for GL ES
cogl-buffer: fix compilation for GL ES

In the frenzy of the last 10mins before API freeze, I obviously forgot
to update the OpenGL path for _cogl_buffer_hints_to_gl_enum(). This
commit fixes this.

Distrotech/clutter,dlespiau/clutter,nobled/clutter,djdeath/clutter,spatulasnout/clutter,djdeath/clutter-android,djdeath/clutter-multithreaded,collects/clutter,kerrickstaley/clutter-vala,jigpu/clutter,collects/clutter,dlespiau/clutter,jigpu/clutter,kerrickstaley/clutter-vala,spatulasnout/clutter,spatulasnout/clutter,Distrotech/clutter,collects/clutter,heysion/clutter-clone,rkudiyarov/clutter_osx,ebassi/clutter,djdeath/clutter,djdeath/clutter,djdeath/clutter-multithreaded,ebassi/clutter,jigpu/clutter,dlespiau/clutter,djdeath/clutter,jigpu/clutter,GNOME/clutter,GNOME/clutter,djdeath/clutter,heysion/clutter-clone,rkudiyarov/clutter_osx,Distrotech/clutter,djdeath/clutter-android,GNOME/clutter,jigpu/clutter,ebassi/clutter,heysion/clutter-clone,ebassi/clutter,Distrotech/clutter,GNOME/clutter,nobled/clutter,collects/clutter,spatulasnout/clutter,GNOME/clutter,spatulasnout/clutter,ebassi/clutter,heysion/clutter-clone,kerrickstaley/clutter-vala,djdeath/clutter-multithreaded,collects/clutter,rkudiyarov/clutter_osx,Distrotech/clutter,djdeath/clutter-android,heysion/clutter-clone,jigpu/clutter,nobled/clutter,djdeath/clutter-android,djdeath/clutter-multithreaded,kerrickstaley/clutter-vala,Distrotech/clutter,djdeath/clutter-android,rkudiyarov/clutter_osx,djdeath/clutter