winsys/svga: fix display corruption after surface_init

When we initialize the buffer surface, do not map the existing storage with DONTBLOCK, leave it as a synchronized map. This patch also sets the surface rebind flag after it is bound to a new buffer and sets the surface buffer pointer accordingly.

This fixes display corruption issue seen with running steam.

Reviewed-by: Neha Bhende bhenden@vmware.com Reviewed-by: Roland Scheidegger sroland@vmware.com

/cc @bhenden