anv: Drop the anv_validate block helper

anv: Drop the anv_validate block helper

Over the course of driver development, we've come up with a number of
different schemes for adding giant blocks of asserts inside the driver.
This one is only being used once in anv_pipeline.c and the way it's
being used actually generates compiler warnings in release builds.  This
commit drops the anv_validate macro and just puts the contents of the
one validation function in side of a "#ifdef DEBUG" guard.

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