Default parameter configuration for CV32E40P

@Silabs-ArjanB has made the following proposal for parameter defaults in verification, documentation and RTL of the CV32E40P as follows:

PULP_XPULP                =  0
PULP_CLUSTER              =  0     
FPU                       =  0
PULP_ZFINX                =  0
NUM_MHPMCOUNTERS          =  0

This would require an update to the core integration section of the User Manual (at least). @Silabs-ArjanB have further suggested that we should add notes/warnings in the User Manual and corresponding assertions in the RTL that PULP_XPULP = 1, PULP_CLUSTER = 1, PULP_ZFINX = 1 have not yet been verified and that the instruction encoding of the PULP instructions will change (in a non-backward compatible manner), as well as that FPU = 1 has not been verified.

For the record, I am strongly in favor of this.