Align performance counters for CV32E40P

[alex96295]

Overview

This PR alignes performance counters in CV32E40P for RTL verification.

Checklist

• Decouple PULP and COREV toolchain (shield with `ifdefs)
• Align and remap performance counters

Note

At the moment, each counter has been associated to one event arbitrarily, following the same approach employed in pulp-runtime. This has almost zero-impact from a user-level viewpoint for what concerns APIs.

Further solutions to make performance counters and events more dynamic can be addressed in future PRs

[NBruschi]

The users should not modify the architecture specific makefile to avoid confusion. I propose something like the following:

PULP_CC      ?= $(shell (basename $(PULP_RISCV_GCC_TOOLCHAIN)/bin/*-gcc))
PULP_LD      ?= $(shell (basename $(PULP_RISCV_GCC_TOOLCHAIN)/bin/*-gcc))
PULP_OBJDUMP ?= $(shell (basename $(PULP_RISCV_GCC_TOOLCHAIN)/bin/*-objdump))
PULP_AR      ?= $(shell (basename $(PULP_RISCV_GCC_TOOLCHAIN)/bin/*-ar))

ifeq ($(PULP_CC), riscv32-corev-elf-gcc)
__COREV_TOOLCHAIN_FLAGS__
else
__PULP_TOOLCHAIN_FLAGS__
endif