i965: split EU defines to brw_eu_defines.h

i965: split EU defines to brw_eu_defines.h

Split out the EU defines from the 'generic' ones, as the former are more
compiler oriented.

With a later commit we'll move brw_eu_defines.h alongside the compiler
infra to src/intel/. Pulling all the defines in there seems overzealous.

Some defines are used by both i965 and the i965 compiler. Those are
moved to brw_eu_defines.h, and annotated accordingly. The i965 users
were updated to have the extre include to indicate that.

With future work we might provide a better, split but for now this seems
reasonable.

Cc: Kenneth Graunke <kenneth@whitecape.org>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>