Revert "Leave only real black box cells"

Revert "Leave only real black box cells"

This reverts commit 43030db5fff285de85096aaf5578b0548659f6b7.

For a synthesis tool, generating EG_LOGIC cells are a good choice, as
they can be furtherly optimized when PnR, although sometimes EG_LOGIC is
not as blackbox as EG_PHY cells (because the latter is more close to the
hardware implementation).

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>