i965: Use intel_get_tile_dims() to get tile masks

i965: Use intel_get_tile_dims() to get tile masks

This will require change in the parameters passed to
intel_miptree_get_tile_masks().

V2: Rearrange the order of parameters. (Ben)
    Change the name to intel_get_tile_masks(). (Topi)

V3: Use temporary variables in intel_get_tile_masks()
    for clarity. Fix mask_y computation.

Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>
Reviewed-by: Chad Versace <chad.versace@intel.com>