anv: Add a layout_to_aux_state helper

anv: Add a layout_to_aux_state helper

This new helper maps VkImageLayout enums to isl_aux_state enums which
are the hardware's concept of image layouts.  We can then use the aux
state to get the fast clear type and the aux usage.  This should yield
no functional change in driver behavior.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Nanley Chery <nanley.g.chery@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/2605>