[doc] Riviera-PRO instructions for Simple System
[doc] Riviera-PRO instructions for Simple System

Fixes #578

Signed-off-by: Greg Chadwick <3e4c3d6d87c017d1a2fa161477653b4039c6b2fb@lowrisc.org>

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