svga: fix constant indices for texcoord scale factors and texture buffer size

svga: fix constant indices for texcoord scale factors and texture buffer size

This patch fixes the ordering of the constant indices for texcoord scale
factor and texture buffer size to match the order they were added to the
constant buffer in svga_get_extra_constants_common().

Tested with MTT piglit, glretrace.

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