i965: fs: Add fixup for textureSize on Gen6/7

i965: fs: Add fixup for textureSize on Gen6/7

V2: Moved up into emit(ir_texture *) to avoid duplication and fix
ordering for Gen7; Gen6 math quirks moved into previous patches.

Tested on Gen6 only; passes all the cube_map_array piglits.

V3: Fixed weird whitespace
V4: Use sampler->type; otherwise broken on arrays of samplers.
v5: Minor style fixes (by anholt)

Signed-off-by: Chris Forbes <chrisf@ijw.co.nz>
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>