svga: fix unnormalized->normalized texture coordinate conversion

svga: fix unnormalized->normalized texture coordinate conversion

Sometimes, converting unnormalized coordinates to normalized
coordinates requires an epsilon value to produce the right texels with
nearest filtering.  Adding 0.0001 to the coordinates when the min/mag
filter is nearest fixes the issue.
Fixes piglit test fbo-blit-scaled-linear

Tested with mtt-piglit, mtt-glretrace

Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Charmaine Lee <charmainel@vmware.com>