mesa: move ElementArrayBufferObj to gl_array_object

mesa: move ElementArrayBufferObj to gl_array_object

According opengl spec 4.2.pdf table 6.12 (Vertex Array Object State) at
page 515, the element buffer object is listed in vertex array object.

So, move the ElementArrayBufferObj inside gl_array_object to make
element buffer object per-vao.

This would fix most of(3 left) intel oglc vao test fail

NOTE: this is a candidate for the 7.11 branch.

Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Reviewed-by: Brian Paul <brianp@vmware.com>