anv/image: Enable specifying a surface's minimum pitch

anv/image: Enable specifying a surface's minimum pitch

This is required to create multiple, horizontally adjacent, max-width
images from one blit2d surface. This is also required for more accurate
width specification of surfaces within a larger surface (which is seen
as the smaller surface's enclosing region).

Note that anv_image_create_info::stride has been unused since commit,
b36938964063a4072abfd779f5607743dbc3b6f1 .

Signed-off-by: Nanley Chery <nanley.g.chery@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>