env.makefile should use MCW_ROOT to refer to caravel_mgmt_soc_litex

[proppy]

caravel_mgmt_soc_litex/verilog/dv/make/env.makefile

Line 30 in 3fee299

export CORE_VERILOG_PATH ?= $(DESIGNS)/caravel_mgmt_soc_litex/verilog

seems to assume this repo is cloned in a directory named caravel_mgmt_soc_litex.

That doesn't seems to be always the case, e.g: caravel_user_project makefile:
https://github.com/efabless/caravel-lite/blob/main/Makefile#L45

Instead env.makefile should probably rely on MCW_ROOT to refer to this path instead of caravel_mgmt_soc_litex.