render: Check GL error for glEGLImageTargetTexture2DOES

It turns out on Mali GPU, sometimes we have some GL errors on
glEGLImageTargetTexture2DOES on some NV12 format image. Before we
figure out a proper fix, call glGetError to clear it.

Signed-off-by: Lepton Wu <lepton@chromium.org>
Reviewed-by: Chia-I Wu <olvaffe@gmail.com>
Part-of: <!793>
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