intel: Enable extensions by just setting the flags

intel: Enable extensions by just setting the flags

Core Mesa already does the dispatch offset remapping for every
function that could possibly ever be supported.  There's no need to
continue using that cruft in the driver.

EXT_blend_logic_op is removed from the list of extensions because
blend factors and separate blend equations are not handled correctly.

Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>