meta: Add rectangle textures to the shader-per-sampler-type table

meta: Add rectangle textures to the shader-per-sampler-type table

Rectangle textures were not necessary for mipmap generation (because
they cannot have mipmaps), but all of the future users of this common
code will need to support rectangle textures.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Eric Anholt <eric@anholt.net>