i965: add support for image AoA

i965: add support for image AoA

V3: clamp array index to the correct size (the size of the current array
rather than the inner array) Francisco Jerez.

V2: avoid useless zero-initialization and addition for the first AoA level,
avoid redundant temporary, make use of type_size_scalar(), rename aoa_size
to element_size, assign the indirect indexing temporary directly to
image.reladdr, and replace while loop with a for loop. All suggested
by Francisco Jerez.

Reviewed-by: Francisco Jerez <currojerez@riseup.net>