svga: Remove unnecessary check for the pre flush bit for setting vertex buffers

This fixes the missing rebind when the can_pre_flush bit
is not set and the vertex buffers are the same as what have been sent.

Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Neha Bhende <bhenden@vmware.com>
Signed-off-by: Charmaine Lee <charmainel@vmware.com>
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
(cherry picked from commit f29b8fde)