Remove outdated documentation
Remove outdated documentation

By now, ibex depends not only on the a clock gating cell, but also on
assert macros and a LFSR; there will be more to come. This removed piece
of documentation was from the early days, when only a clock gating cell
was to be provided (and we didn't ship one).

Today, users need to either use FuseSoC, or run fusesoc on the simple
system and "harvest" the resulting files if they want to copy-paste Ibex
into their build system. That's not ideal, but not something we can very
easily fix -- so let's remove the outdated documentation first to at
least reduce the confusion.

lowRISC/ibex,lowRISC/ibex,AmbiML/ibex,AmbiML/ibex,AmbiML/ibex,lowRISC/ibex,lowRISC/ibex,AmbiML/ibex