make: Rework clean target in database/Makefile
make: Rework clean target in database/Makefile

 * Have targets for only removing the database and not the harness /
   gridinfo tool.
 * Have seperate targets for cleaning each database.

Signed-off-by: Tim 'mithro' Ansell <b1c1d8736f20db3fb6c1c66bb1455ed43909f0d8@mith.ro>

SymbiFlow/prjxray,SymbiFlow/prjxray,SymbiFlow/prjxray,SymbiFlow/prjxray,SymbiFlow/prjxray