anv: Sanitize Image extents and offsets

anv: Sanitize Image extents and offsets

Prepare Image extents and offsets for internal consumption by assigning
the default values implicitly defned by the spec. Fixes textures on
several Vulkan demos in which the VkImageCopy depth is set to zero when
copying a 2D image.

v2 (Jason Ekstrand):
   Replace "prep" with "sanitize"
   Make function static inline
   Pass structs instead of pointers

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