svga: use pipe_sampler_view_release() in svga_cleanup_tss_binding()

svga: use pipe_sampler_view_release() in svga_cleanup_tss_binding()

Fixes a crash when the Redway3D Turbine demo exits.  We've made this
change in other places in the past.  The root issue is texture objects
are being shared by multiple contexts and sampler views get shared too.
Sampler views have a context pointer and if that context gets deleted
we may try to reference that context when finally deleting the sampler
view.

pipe_sampler_view_release() avoids this problem because it takes
an explicit context.

Reviewed-by: Zack Rusin <zackr@vmware.com>