mstatus fs addition & bug corrections

Created by: pascalgouedo

Issue #170 (closed) correction: Adding MSTATUS.FS/SD

Issue #724 (closed) correction: Illegal exception for unknown F instructions.

Move from PULP_ZFINX to ratified v1.0 ZFINX. Issue #725 (closed) correction: Illegal exception for FMV/FLW/FSW when ZFINX. Updated MISA value and make MSTATUS.FS/SD ZFINX dependent.

Move PULP_ZFINX parameter to ZFINX in all RTL files. Removed PULP_XPULP, PULP_CLUSTER, FPU, PULP_ZFINX assertions.

Issue #174 (closed) and #169 (closed) correction: Flush instructions following CSRW to FRM/FCSR.

Issue #741 (closed) correction: Illegal exception when CSRW to uhartid and privlv.

Renamed cv32e40p_wrapper to cv32e40p_top and updated all files from wrapper to top instantiation.

Added in cv32e40p_top a clock gating cell for FPU.

Updates to allow MSTATUS.FS and SD comparison with Imperas ISS.

Moved PULP_XPULP to COREV_PULP and PULP_CLUSTER to COREV_CLUSTER.