Renamed riscv_core to cv32e40p_core

Created by: Silabs-ArjanB

RTL update for https://github.com/openhwgroup/core-v-docs/issues/51

Only the module renaming was done. The other topics raised (e.g. license, ifdefs) are not related to documentation and will be handled separately.

Signed-off-by: Arjan Bink Arjan.Bink@silabs.com