anv: Get rid of the stub() macros

anv: Get rid of the stub() macros

Except for a few unimplemented things on gen7, we don't really have
stubs anymore so we should drop this.  This commit replaces the few gen7
stub() calls with explicitly labeled finishme's and makes the sparse
binding stuff silently no-op or return a FEATURE_NOT_PRESENT error.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>